MEDICAL

CHEMISTRY AND
BIOCHEMISTRY
FACULTY OF DENTAL MEDICINE
DR. AKSU SAMET
 INTRODUCTION TO CHEMISTRY
• ALL OF THE OBJECTS AROUND YOU
• THIS BOOK, YOUR PEN OR PENCIL, AND
• THE THINGS OF NATURE SUCH AS ROCKS, WATER, AND PLANT AND
ANIMAL SUBSTANCES
• CONSTITUTE THE MATTER OF THE UNIVERSE.

• WE CAN DEFINE CHEMISTRY AS THE,

SCIENCE OF THE COMPOSITION AND STRUCTURE OF
MATERIALS AND OF THE CHANGES THAT MATERIALS UNDERGO.
 MODERN CHEMISTRY
• FOR THOUSANDS OF YEARS, HUMAN BEINGS HAVE FASHIONED
NATURAL MATERIALS INTO USEFUL PRODUCTS.
• MODERN CHEMISTRY
• AFTER THE DISCOVERY OF FIRE, PEOPLE BEGAN TO NOTICE
CHANGES IN CERTAIN ROCKS AND MINERALS EXPOSED TO HIGH
TEMPERATURES.
• DEVELOPMENT OF CERAMICS, GLASS, AND METALS, WHICH
TODAY ARE AMONG OUR MOST USEFUL MATERIALS.
• CHEMISTS COULD ALSO CORRELATE MOLECULAR STRUCTURE WITH THE
CHARACTERISTICS OF MATERIALS AND SO BEGIN TO FASHION MATERIALS
WITH SPECIAL CHARACTERISTICS.
• EXAMPLES:
• THE LIQUID-CRYSTAL DISPLAYS (LCDS) THAT ARE USED ON EVERYTHING FROM
WATCHES AND CELL PHONES TO COMPUTER MONITORS AND TELEVISIONS –
APPLICATION THAT DEPENDS ON THE SPECIAL CHARACTERISTICS OF
MATERIALS
A cell phone that
uses a liquid
crystal
Display.
• CHEMISTS CONTINUE TO DEVELOP NEW MATERIALS AND TO DISCOVER NEW
PROPERTIES OF OLD ONES.
• NOT ONLY IS OPTICAL-FIBER CABLE CHEAPER AND LESS BULKY THAN COPPER CABLE
CARRYING THE SAME INFORMATION, BUT THROUGH THE USE OF DIFFERENT COLORS
OF LIGHT, OPTICAL-FIBER CABLE CAN CARRY VOICE, DATA, AND VIDEO INFORMATION
AT THE SAME TIME.
• BIOCHEMISTS AND MOLECULAR BIOLOGISTS—SCIENTISTS WHO STUDY THE
MOLECULAR BASIS OF LIVING ORGANISMS—HAVE MADE A REMARKABLE FINDING: ALL
FORMS OF LIFE APPEAR TO SHARE MANY OF THE SAME MOLECULES AND MOLECULAR
PROCESSES.
DNA contains the
Optical fibers hereditary
A bundle of optical information of
fibers that can be used an organism that
to transmit data via is passed on
pulses of light. from one
generation to the
next.
 THE ATOMIC AND MOLECULAR
PERSPECTIVE OF CHEMISTRY
• CHEMISTRY IS THE STUDY OF THE PROPERTIES AND BEHAVIOR OF MATTER.
• MATTER IS THE PHYSICAL MATERIAL OF THE UNIVERSE; IT IS ANYTHING THAT HAS
MASS AND OCCUPIES SPACE.
• TREMENDOUS VARIETY OF MATTER IN OUR WORLD IS DUE TO COMBINATIONS
OF ONLY ABOUT 100 SUBSTANCES CALLED ELEMENTS.
• ATOMS, THE ALMOST INFINITESIMALLY SMALL BUILDING BLOCKS OF MATTER.
• IN MOLECULES, TWO OR MORE ATOMS ARE JOINED TOGETHER IN SPECIFIC
SHAPES.
 FIGURE . MOLECULAR MODELS. THE WHITE, BLACK, AND RED SPHERES
REPRESENT ATOMS OF HYDROGEN, CARBON, AND OXYGEN, RESPECTIVELY.
=H =O =C

Oxygen
Water

Ethanol Ethylene glycol Aspirin

 WHY STUDY CHEMISTRY?
• USING CHEMISTRY,
• WE HAVE DISCOVERED PHARMACEUTICAL CHEMICALS THAT ENHANCE HEALTH AND PROLONG
LIVES.
• WE HAVE INCREASED FOOD PRODUCTION THROUGH THE USE OF FERTILIZERS AND PESTICIDES,
• WE HAVE DEVELOPED PLASTICS AND OTHER MATERIALS USED IN ALMOST EVERY FACET OF OUR
LIVES,
• FROM ELECTRONICS TO SPORTING EQUIPMENT TO BUILDING CONSTRUCTION.
• UNFORTUNATELY, SOME CHEMICALS CAN HARM OUR HEALTH OR THE ENVIRONMENT. AS
EDUCATED CITIZENS AND CONSUMERS, IT IS IN OUR BEST INTEREST TO UNDERSTAND THE
PROFOUND EFFECTS, BOTH POSITIVE AND NEGATIVE, THAT CHEMICALS HAVE ON OUR LIVES
AND TO STRIKE AN INFORMED BALANCE ABOUT THEIR USES.
CHEMISTRY GREATLY IMPACTS OUR DAILY LIVES.
 WHY STUDY CHEMISTRY?
• YOUR MAJOR MIGHT BE CHEMISTRY, BUT IT COULD BE BIOLOGY, ENGINEERING,
PHARMACY, AGRICULTURE, GEOLOGY, OR SOME OTHER FIELD.
• WHY DO SO MANY SUBJECTS SHARE AN ESSENTIAL TIE TO CHEMISTRY? THE ANSWER IS
THAT CHEMISTRY IS THE CENTRAL SCIENCE.

Chemistry helps understand the world around us.(a) Solar cells are made of silicon. (b) A
Renaissance painting, Young Girl Reading, by Vittore Carpaccio (1472–1526), uses pigments
that keep heir color for years.(c) The light from this firefly is the result of a chemical reaction
within the animal.
 WHO ARE CHEMISTS, AND WHAT DO THEY
DO?
• PEOPLE WHO HAVE DEGREES IN CHEMISTRY HOLD A VARIETY OF
POSITIONS IN INDUSTRY, GOVERNMENT AND ACADEMIA.
• WORK AS LABORATORY CHEMISTS, DEVELOPING NEW
PRODUCTS, ANALYZING MATERIALS, ETC..
 CLASSIFICATIONS OF MATTER

• TWO PRINCIPAL WAYS OF CLASSIFYING MATTER ARE

1. ACCORDING TO PHYSICAL STATE (GAS, LIQUID, OR SOLID)
2. ACCORDING TO COMPOSITION (ELEMENT, COMPOUND, OR MIXTURE).
 PHYSICAL STATES OF MATTER
• COMMONLY, A GIVEN KIND OF MATTER EXISTS IN DIFFERENT
PHYSICAL FORMS UNDER DIFFERENT CONDITIONS.
• WATER, FOR EXAMPLE, EXISTS AS ICE (SOLID WATER), AS LIQUID
WATER, AND AS STEAM. A SAMPLE OF MATTER CAN BE A GAS, A
LIQUID, OR A SOLID.
 SOLID STATE
• BOTH A DEFINITE SHAPE AND A DEFINITE VOLUME.
• THE MOLECULES ARE HELD TIGHTLY TOGETHER, USUALLY
IN FIXED POSITIONS.
• THE DISTANCES BETWEEN MOLECULES ARE SIMILAR IN
THE LIQUID AND SOLID STATES, BUT THE TWO STATES
DIFFER IN HOW FREE THE MOLECULES ARE TO MOVE
AROUND.
• CHANGES IN TEMPERATURE AND/OR PRESSURE CAN
LEAD TO CONVERSION FROM ONE STATE OF MATTER TO
ANOTHER – EX: ICE MELTING OR WATER VAPOR
CONDENSING.
LIQUID STATE
• A LIQUID HAS A DISTINCT
VOLUME, IT ASSUMES THE SHAPE
OF THE CONTAINER IT
OCCUPIES.
• IN A LIQUID THE MOLECULES ARE
PACKED CLOSELY TOGETHER BUT
STILL MOVE RAPIDLY.
• THE RAPID MOVEMENT ALLOWS
THE MOLECULES TO SLIDE OVER
ONE ANOTHER; THUS, A LIQUID
POURS EASILY.
GAS (ALSO KNOWN AS VAPOR) STATE
• HAS NO FIXED VOLUME OR SHAPE;
• IT CONFORMS TO THE VOLUME AND SHAPE OF
ITS CONTAINER.
• IN A GAS THE MOLECULES ARE FAR APART AND
• MOVING AT HIGH SPEEDS, COLLIDING
REPEATEDLY WITH ONE ANOTHER AND WITH THE
WALLS OF THE CONTAINER.
• COMPRESSING A GAS DECREASES THE AMOUNT
OF SPACE BETWEEN MOLECULES AND INCREASES
THE
• FREQUENCY OF COLLISIONS BETWEEN
MOLECULES BUT DOES NOT ALTER THE SIZE OR
SHAPE OF THE MOLECULES.
CLASSIFICATION ACCORDING COMPOSITION
OF MATTER
 PURE SUBSTANCES
A PURE SUBSTANCE IS MATTER THAT HAS DISTINCT PROPERTIES AND A
COMPOSITION THAT DOES NOT VARY FROM SAMPLE TO SAMPLE.
OR
A SUBSTANCE IS A KIND OF MATTER THAT CANNOT BE SEPARATED INTO OTHER
KINDS OF MATTER BY ANY PHYSICAL PROCESS.

ALL SUBSTANCES ARE EITHER ELEMENTS OR COMPOUNDS.

 ELEMENTS
• MILLIONS OF SUBSTANCES HAVE BEEN CHARACTERIZED BY CHEMISTS. OF THESE, A VERY SMALL
NUMBER ARE KNOWN AS ELEMENTS, FROM WHICH ALL OTHER SUBSTANCES ARE MADE.
• LAVOISIER WAS THE FIRST TO ESTABLISH AN EXPERIMENTALLY USEFUL DEFINITION OF AN ELEMENT.

• ELEMENTS ARE SUBSTANCES THAT CANNOT BE DECOMPOSED INTO SIMPLER SUBSTANCES.

• EACH ELEMENT IS COMPOSED OF ONLY ONE KIND OF ATOM.
• CURRENTLY, 118 ELEMENTS ARE KNOWN. FOR EXAMPLE, OXYGEN, SILICON, ALUMINUM, IRON,
CALCIUM, CARBON
Some elements
Center: Sulfur. From upper right,
clockwise:
Arsenic, iodine, magnesium,
bismuth,
mercury.
 COMPOUNDS
• MOST SUBSTANCES ARE COMPOUNDS. A COMPOUND IS A SUBSTANCE COMPOSED
• OF TWO OR MORE ELEMENTS CHEMICALLY COMBINED. THEY CONTAIN TWO OR MORE KINDS
OF ATOMS.
• WATER, FOR EXAMPLE, IS A COMPOUND COMPOSED OF TWO ELEMENTS: HYDROGEN AND
OXYGEN.

Hydrogen gas, H2
Oxygen gas, O2

Water, H2O
 MIXTURES
• MIXTURES ARE COMBINATIONS OF TWO OR MORE SUBSTANCES IN WHICH EACH
SUBSTANCE RETAINS ITS CHEMICAL IDENTITY. THE COMPOSITION OF A MIXTURE CAN
VARY.
• THE SUBSTANCES MAKING UP A MIXTURE ARE CALLED COMPONENTS OF THE MIXTURE.
• A MIXTURE IS A MATERIAL HAT CAN BE SEPARATED BY PHYSICAL MEANS INTO TWO OR
MORE SUBSTANCES.
• HETEROGENEOUS AND HOMOGENEOUS MIXTURES -. MIXTURES THAT ARE UNIFORM
THROUGHOUT ARE HOMOGENEOUS. EX: AIR ,SALT, SUGAR, AND MANY OTHER
SUBSTANCES DISSOLVE IN WATER.
• HOMOGENEOUS MIXTURES ARE ALSO CALLED SOLUTIONS (SOLIDS, LIQUIDS, OR GASES).
 HETEROGENEOUS MIXTURES
• HETEROGENEOUS MIXTURE IS A MIXTURE THAT CONSISTS OF PHYSICALLY
DISTINCT PARTS, EACH WITH DIFFERENT PROPERTIES.
• DO NOT HAVE THE SAME COMPOSITION, PROPERTIES

A heterogeneous mixture
Left: The mixture on the watch glass consists of potassium dichromate (orangecrystals) and iron filings.
Right: A magnet separates the iron filings from the mixture.
 HOMOGENEOUS MIXTURES
• MIXTURES THAT ARE UNIFORM THROUGHOUT ARE HOMOGENEOUS.
EX: AIR ,SALT, SUGAR, AND MANY OTHER SUBSTANCES DISSOLVE IN WATER.
• HOMOGENEOUS MIXTURES ARE ALSO CALLED SOLUTIONS (SOLIDS, LIQUIDS, OR
GASES).
Homogeneous mixtures
are called solutions. Many
substances, including the
blue solid shown here
[copper(II) sulfate],
dissolve in water to form
solutions.
 PROPERTIES OF MATTER
• WE CHARACTERIZE OR IDENTIFY A MATERIAL BY ITS VARIOUS PROPERTIES, WHICH MAY BE
EITHER PHYSICAL OR CHEMICAL.

PHYSICAL PROPERTIES
• A PHYSICAL PROPERTY IS A CHARACTERISTIC THAT CAN BE OBSERVED FOR A MATERIAL
WITHOUT CHANGING ITS CHEMICAL IDENTITY.
• EXAMPLES ARE PHYSICAL STATE (SOLID, LIQUID, OR GAS), MELTING POINT, AND COLOR.

PHYSICAL CHANGE
• A PHYSICAL CHANGE IS A CHANGE IN THE FORM OF MATTER BUT NOT IN ITS CHEMICAL
IDENTITY.
• CHANGES OF PHYSICAL STATE ARE EXAMPLES OF PHYSICAL CHANGES. THE PROCESS OF
DISSOLVING ONE MATERIAL IN ANOTHER IS A FURTHER EXAMPLE OF A PHYSICAL CHANGE.
 CHEMICAL PROPERTIES
• A CHEMICAL PROPERTY IS A CHARACTERISTIC OF A MATERIAL INVOLVING ITS CHEMICAL CHANGE.
• A CHEMICAL PROPERTY OF IRON IS ITS ABILITY TO REACT WITH OXYGEN TO PRODUCE RUST. WITHOUT
CHANGING THE IDENTITY AND COMPOSITION OF THE SUBSTANCE.
• EX: COLOR, ODOR, DENSITY, MELTING POINT, BOILING POINT, AND HARDNESS.

• CHEMICAL CHANGE
• A CHEMICAL CHANGE, OR CHEMICAL REACTION, IS A CHANGE IN WHICH ONE OR MORE
KINDS OF MATTER ARE TRANSFORMED INTO A NEW KIND OF MATTER OR SEVERAL NEW KINDS OF
MATTER.
• THE RUSTING OF IRON, DURING WHICH IRON COMBINES WITH OXYGEN IN THE AIR TO FORM A NEW
MATERIAL CALLED RUST, IS A CHEMICAL CHANGE. THE ORIGINAL MATERIALS (IRON AND OXYGEN)
COMBINE CHEMICALLY AND CANNOT BE SEPARATED BY ANY PHYSICAL MEANS.
• INTENSIVE PROPERTIES
• THEY DO NOT DEPEND ON THE AMOUNT OF SAMPLE. EX:
TEMPERATURE AND MELTING POINT
• EXTENSIVE PROPERTIES
• DEPEND ON THE AMOUNT OF SAMPLE EX: BEING MASS AND
VOLUME.
 LAW OF CONSERVATION OF MASS
• MODERN CHEMISTRY EMERGED IN THE EIGHTEENTH CENTURY, WHEN CHEMISTS BEGAN TO
USE THE
BALANCE SYSTEMATICALLY AS A TOOL IN RESEARCH.
BALANCES MEASURE MASS, WHICH IS THE QUANTITY OF MATTER IN A MATERIAL .
• MATTER IS THE GENERAL TERM FOR THE MATERIAL THINGS AROUND US; WE CAN DEFINE IT
AS WHATEVER OCCUPIES SPACE AND CAN BE PERCEIVED BY OUR SENSES.
A modern single-pan balance. The mass of
the material on the pan appears on the
digital readout.
• ANTOINE LAVOISIER (1743–1794), A FRENCH CHEMIST, WAS ONE OF
THE FIRST TO INSIST ON THE USE OF THE BALANCE IN CHEMICAL
RESEARCH.
• BY WEIGHING SUBSTANCES BEFORE AND AFTER CHEMICAL CHANGE,
HE DEMONSTRATED THE LAW OF CONSERVATION OF MASS,
• THE TOTAL MASS REMAINS CONSTANT DURING A CHEMICAL CHANGE
(CHEMICAL REACTION).

Mercury oxygen mercury(II) oxide

ATOMS, MOLECULES,
AND IONS
ATOMIC THEORY OF MATTER
 POSTULATES OF DALTON’S ATOMIC THEORY
THE MAIN POINTS OF DALTON’S ATOMIC THEORY, AN EXPLANATION OF THE
STRUCTURE OF MATTER IN TERMS OF DIFFERENT COMBINATIONS OF VERY
SMALL PARTICLES, ARE GIVEN BY THE FOLLOWING POSTULATES:
• 1. ALL MATTER IS COMPOSED OF INDIVISIBLE ATOMS.
AN ATOM IS AN EXTREMELY SMALL PARTICLE OF MATTER THAT RETAINS ITS
IDENTITY DURING CHEMICAL REACTIONS.

• .
 POSTULATES OF DALTON’S ATOMIC THEORY
.

• 2. AN ELEMENT IS A TYPE OF MATTER COMPOSED OF ONLY ONE KIND OF

ATOM, EACH ATOM OF A GIVEN KIND HAVING THE SAME PROPERTIES.
• 3. A COMPOUND IS A TYPE OF MATTER COMPOSED OF ATOMS OF TWO OR
MORE ELEMENTS CHEMICALLY COMBINED IN FIXED PROPORTIONS.
• 4. A CHEMICAL REACTION CONSISTS OF THE REARRANGEMENT OF THE
ATOMS PRESENT IN THE REACTING SUBSTANCES TO GIVE NEW CHEMICAL
COMBINATIONS PRESENT IN THE SUBSTANCES FORMED BY THE REACTION.
ATOMS ARE NOT CREATED, DESTROYED, OR BROKEN INTO SMALLER PARTICLES
BY ANY CHEMICAL REACTION.
 DEDUCTIONS FROM DALTON’S ATOMIC
THEORY
ATOMIC THEORY ALSO EXPLAINS TWO LAWS WE CONSIDERED EARLIER. ONE
OF THESE IS THE LAW OF CONSERVATION OF MASS,
• BY POSTULATE 2, EVERY ATOM HAS A DEFINITE MASS. BECAUSE A CHEMICAL
REACTION ONLY REARRANGES THE CHEMICAL COMBINATIONS OF ATOMS
(POSTULATE 4), THE MASS MUST REMAIN CONSTANT.
• THE LAW OF DEFINITE PROPORTIONS (CONSTANT COMPOSITION).
POSTULATE 3 DEFINES A COMPOUND AS A TYPE OF MATTER CONTAINING
THE ATOMS OF TWO OR MORE ELEMENTS IN DEFINITE PROPORTIONS.
 DISCOVERY OF THE ELECTRON
• IN 1897 THE BRITISH PHYSICIST J. J. THOMSON CONDUCTED A SERIES OF
EXPERIMENTS THAT SHOWED THAT ATOMS WERE NOT INDIVISIBLE
PARTICLES. PROVED THAT AN ATOM CAN BE DIVIDED INTO SMALLER PARTS
• WHILE EXPERIMENTING WITH CATHODE-RAY TUBES, DISCOVERED
CORPUSCLES, WHICH WERE LATER CALLED ELECTRONS
• IN THIS APPARATUS- TWO ELECTRODES FROM A HIGH-VOLTAGE SOURCE INTO A GLASS TUBE FROM
WHICH THE AIR HAS BEEN EVACUATED.
• THE NEGATIVE ELECTRODE IS CALLED THE CATHODE; THE POSITIVE ONE, THE ANODE.
• EXPERIMENTS SHOWED THAT THIS LIGHT IS CAUSED BY THE INTERACTION OF THE GLASS WITH CATHODE
RAYS, WHICH ARE RAYS THAT ORIGINATE FROM THE CATHODE.
• AFTER THE CATHODE RAYS LEAVE THE NEGATIVE ELECTRODE, THEY MOVE TOWARD THE ANODE, WHERE
SOME RAYS PASS THROUGH A HOLE TO FORM A BEAM. THIS BEAM BENDS AWAY FROM THE
NEGATIVELY CHARGED PLATE AND TOWARD THE POSITIVELY CHARGED PLATE.
• THOMSON SHOWED THAT THE CHARACTERISTICS OF CATHODE RAYS ARE INDEPENDENT OF THE
MATERIAL MAKING UP THE CATHODE. FROM SUCH EVIDENCE, HE CONCLUDED THAT A CATHODE RAY
CONSISTS OF A BEAM OF NEGATIVELY CHARGED PARTICLES (OR ELECTRONS) AND THAT ELECTRONS ARE
CONSTITUENTS OF ALL MATTER.
•Stated that the atom is neutral
•In 1897, proposed the Plum Pudding Model which
states that atoms mostly consist of positively charged
material with negatively charged particles (electrons)
located throughout the positive material
•Won a Nobel Prize
• THOMSON COULD ALSO CALCULATE THE RATIO OF THE ELECTRON’S MASS, ME, TO ITS
ELECTRIC CHARGE, E. HE COULD NOT OBTAIN EITHER THE MASS OR THE CHARGE SEPARATELY.
• IN 1909 THE U.S. PHYSICIST ROBERT MILLIKAN PERFORMED A SERIES OF INGENIOUS
EXPERIMENTS IN WHICH HE OBTAINED THE CHARGE ON THE ELECTRON BY OBSERVING HOW
A CHARGED DROP OF OIL FALLS IN THE PRESENCE AND IN THE ABSENCE OF AN ELECTRIC FIELD
(FIGURE 2.6).
35
 THE NUCLEAR MODEL OF THE ATOM
• ERNEST RUTHERFORD (1871–1937), A BRITISH PHYSICIST, PUT FORTH THE IDEA OF THE
NUCLEAR MODEL OF THE ATOM IN 1911,
• IN 1909, PERFORMED THE GOLD FOIL EXPERIMENT
 THE NUCLEAR MODEL OF THE ATOM
THESE SCIENTISTS OBSERVED THE EFFECT OF BOMBARDING THIN GOLD FOIL (AND OTHER METAL
FOILS) WITH ALPHA RADIATION FROM RADIOACTIVE SUBSTANCES SUCH AS URANIUM.
RUTHERFORD HAD ALREADY SHOWN THAT ALPHA RAYS CONSIST OF POSITIVELY CHARGED
PARTICLES.
• ACCORDING TO RUTHERFORD’S MODEL, MOST OF THE MASS OF THE ATOM (99.95% OR
MORE) IS CONCENTRATED IN A POSITIVELY CHARGED CENTER, OR NUCLEUS, AROUND WHICH
THE NEGATIVELY CHARGED ELECTRONS MOVE. ALTHOUGH MOST OF THE MASS OF AN ATOM
IS IN ITS NUCLEUS, THE NUCLEUS OCCUPIES ONLY A VERY SMALL PORTION OF THE SPACE OF
THE ATOM. NUCLEI HAVE DIAMETERS OF ABOUT 10 -15 MM10-3 PM.
 NUCLEAR STRUCTURE; ISOTOPES
• IN 1932 THE BRITISH PHYSICIST JAMES CHADWICK (1891–1974) SHOWED THAT THIS
PENETRATING RADIATION CONSISTS OF NEUTRAL PARTICLES, OR NEUTRONS. THE NEUTRON
IS A NUCLEAR PARTICLE HAVING A MASS ALMOST IDENTICAL TO THAT OF THE PROTON BUT
NO ELECTRIC CHARGE. Mass Charge Charge
Particle
(g) (Coulombs) (units)

Electron (e-) 9.1 x 10-28 -1.6 x 10-19 -1

Proton (p) 1.67 x 10-24 +1.6 x 10-19 +1

Neutron (n) 1.67 x 10-24 0 0

mass p = mass n = 1840 x mass e-
• WE CHARACTERIZE A NUCLEUS BY ITS ATOMIC NUMBER (Z) ; MASS
NUMBER (A) IS THE TOTAL NUMBER OF PROTONS AND NEUTRONS IN A
NUCLEUS.

A nuclide is an atom characterized by a definite atomic number and

mass number.
ISOTOPES ARE ATOMS WHOSE NUCLEI HAVE THE SAME
ATOMIC NUMBER BUT DIFFERENT MASS NUMBERS; THAT
IS, THE NUCLEI HAVE THE SAME NUMBER OF PROTONS
BUT DIFFERENT NUMBERS OF NEUTRONS.
QUANTUM THEORY OF ATOM
THE BOHR THEORY OF THE HYDROGEN
ATOM

42
 THE BOHR THEORY OF THE HYDROGEN
ATOM
• BOHR’S POSTULATES
• 1. ENERGY-LEVEL POSTULATE AN ELECTRON CAN HAVE ONLY SPECIFIC ENERGY VALUES IN
AN ATOM, WHICH ARE CALLED ITS ENERGY LEVELS. THEREFORE, THE ATOM ITSELF CAN HAVE
ONLY SPECIFIC TOTAL ENERGY VALUES.

• RH IS A CONSTANT (EXPRESSED IN ENERGY UNITS) WITH THE

• VALUE 2.179 X 10-18 J.
• DIFFERENT VALUES OF THE POSSIBLE ENERGIES OF
THE ELECTRON ARE OBTAINED BY PUTTING INDIFFERENT VALUES OF
N =1, 2, 3, PRINCIPAL QUANTUM NUMBER.
43
• 2. TRANSITIONS BETWEEN ENERGY LEVELS AN ELECTRON IN AN ATOM CAN
CHANGE ENERGY ONLY BY GOING FROM ONE ENERGY LEVEL TO ANOTHER
ENERGY LEVEL. BY SO DOING, THE ELECTRON UNDERGOES A TRANSITION.
• ACCORDING TO BOHR, THE EMISSION OF LIGHT FROM AN ATOM OCCURS AS
FOLLOWS. AN ELECTRON IN A HIGHER ENERGY LEVEL (INITIAL ENERGY LEVEL, EI)
UNDERGOES A TRANSITION TO A LOWER ENERGY LEVEL (FINAL ENERGY LEVEL,
EF) (SEE FIGURE 7.10). IN THIS PROCESS, THE ELECTRON LOSES ENERGY, WHICH
IS EMITTED AS A PHOTON
• IN GENERAL, THE ENERGY OF THE EMITTED PHOTON, HV, EQUALS THE POSITIVE
ENERGY LOST BY THE ATOM (E):

44
• BOHR’S THEORY EXPLAINS NOT ONLY THE EMISSION BUT ALSO THE
ABSORPTION OF LIGHT.
• WHEN AN ELECTRON IN THE HYDROGEN ATOM UNDERGOES A
TRANSITION FROM N 3 TO N 2, A PHOTON OF RED LIGHT
(WAVELENGTH 656 NM) IS EMITTED.
• BOHR’S THEORY WAS UNSUCCESSFUL, HOWEVER, IN
ACCOUNTING FOR THE DETAILS OF ATOMIC STRUCTURE AND IN
PREDICTING ENERGY LEVELS FOR ATOMS OTHER THAN HYDROGEN.
FURTHER UNDERSTANDING OF ATOMIC STRUCTURE REQUIRED
OTHER THEORETICAL DEVELOPMENTS.
45
•
QUANTUM MECHANICS
CURRENT IDEAS ABOUT ATOMIC STRUCTURE DEPEND ON THE PRINCIPLES OF QUANTUM MECHANICS, A THEORY
THAT APPLIES TO SUBMICROSCOPIC (THAT IS, EXTREMELY SMALL) PARTICLES OF MATTER, SUCH AS ELECTRONS. THE
DEVELOPMENT OF THIS THEORY WAS STIMULATED BY THE DISCOVERY OF THE DE BROGLIE RELATION.
• DE BROGLIE RELATION
• ACCORDING TO EINSTEIN, LIGHT HAS NOT ONLY WAVE PROPERTIES, WHICH WE CHARACTERIZE BY FREQUENCY
AND WAVELENGTH, BUT ALSO PARTICLE PROPERTIES. FOR EXAMPLE, A PARTICLE OF LIGHT, THE PHOTON, HAS A
DEFINITE ENERGY E H. ONE CAN ALSO SHOW THAT THE PHOTON HAS MOMENTUM. (THE MOMENTUM OF A
PARTICLE IS THE PRODUCT OF ITS MASS AND SPEED.) THIS MOMENTUM, MC, IS RELATED TO THE WAVELENGTH OF
THE LIGHT: MC H/ OR H/MC.
• IN 1923 THE FRENCH PHYSICIST LOUIS DE BROGLIE REASONED THAT IF LIGHT (CONSIDERED
• AS A WAVE) EXHIBITS PARTICLE ASPECTS, THEN PERHAPS PARTICLES OF MATTER SHOW CHARACTERISTICS
• OF WAVES UNDER THE PROPER CIRCUMSTANCES. HE THEREFORE POSTULATED THAT A
• PARTICLE OF MATTER OF MASS M AND SPEED V HAS AN ASSOCIATED WAVELENGTH, BY ANALOGY
• WITH LIGHT. THE EQUATION H/MV IS CALLED THE DE BROGLIE RELATION.

46
 WAVE FUNCTIONS

• DE BROGLIE’S RELATION APPLIES QUANTITATIVELY ONLY TO PARTICLES IN A FORCE-FREE

ENVIRONMENT.
• IT CANNOT BE APPLIED DIRECTLY TO AN ELECTRON IN AN ATOM, WHERE THE ELECTRON IS
• SUBJECT TO THE ATTRACTIVE FORCE OF THE NUCLEUS. BUT IN 1926 ERWIN SCHRODINGER,
GUIDED
• BY DE BROGLIE’S WORK, DEVISED A THEORY THAT COULD BE USED TO FIND THE WAVE
PROPERTIES
• OF ELECTRONS IN ATOMS AND MOLECULES. THE BRANCH OF PHYSICS THAT MATHEMATICALLY
• DESCRIBES THE WAVE PROPERTIES OF SUBMICROSCOPIC PARTICLES IS CALLED QUANTUM
MECHANICS
• OR WAVE MECHANICS
47
 QUANTUM NUMBERS AND ATOMIC
ORBITALS
• ACCORDING TO QUANTUM MECHANICS, EACH ELECTRON IN AN ATOM IS DESCRIBED BY FOUR
DIFFERENT
• QUANTUM NUMBERS, THREE OF WHICH (N, L, AND ML) SPECIFY THE WAVE FUNCTION THAT
• GIVES THE PROBABILITY OF FINDING THE ELECTRON AT VARIOUS POINTS IN SPACE. < A WAVE
FUNCTION
• FOR AN ELECTRON IN AN ATOM IS CALLED AN ATOMIC ORBITAL.AN ATOMIC ORBITAL IS
PICTUREDQUALITATIVELY BY DESCRIBING THE REGION OF SPACE WHERE THERE IS HIGH PROBABILITY
OF FINDING
• THE ELECTRONS. THE ATOMIC ORBITAL SO PICTURED HAS A DEFINITE SHAPE. A FOURTH QUANTUM
• NUMBER (MS) REFERS TO A MAGNETIC PROPERTY OF ELECTRONS CALLED SPIN. WE FIRST LOOK
• AT QUANTUM NUMBERS, THEN AT ATOMIC ORBITALS.

48
 QUANTUM NUMBERS

A QUANTUM NUMBER IS A NUMBER THAT SPECIFIES THE

PROPERTIES OF ELECTRONS

1. PRINCIPAL QUANTUM NUMBER (N)

2. ANGULAR (SECONDARY) QUANTUM NUMBER (L)
3. MAGNETIC QUANTUM NUMBER (ML)
4.SPIN QUANTUM NUMBER (MS)
 ELECTRON CONFIGURATION
• WOLFGANG ERNST PAULI
• PAULI `S PRINCIPLE:
• ``IN THE SAME ATOM, TWO ELECTRONS MAY NOT HAVE IDENTICAL SETS OF ALL
QUANTUM NUMBER``
• THE AUFBAU PRINCIPLE
• ``THE LOWEST ENERGY ORBITAL'S ARE FILLED FIRST``
 ATOMIC ORBITAL SHAPES
• AN S ORBITAL HAS A SPHERICAL SHAPE, THOUGH SPECIFIC DETAILS OF THE PROBABILITY
DISTRIBUTION DEPEND ON THE VALUE OF N.

54
 ATOMIC ORBITAL SHAPES
• THERE ARE THREE P ORBITALS IN EACH P SUBSHELL. ALL P ORBITALS HAVE THE SAME BASIC
SHAPE (TWO LOBES ARRANGED ALONG A STRAIGHT LINE WITH THE NUCLEUS BETWEEN
THE LOBES) BUT DIFFER IN THEIR ORIENTATIONS IN SPACE.

55
 ATOMIC ORBITAL SHAPES
• THERE ARE FIVE D ORBITALS, WHICH HAVE MORE COMPLICATED SHAPES THAN DO S AND
P ORBITALS

56
ELECTRON CONFIGURATION AND
PERIODICITY
ELECTRONIC STRUCTURE OF
ATOM
 IN PREVIOUS CHAPTER

• AN ELECTRON IN AN ATOM HAS FOUR QUANTUM NUMBERS—N, L,

ML, AND MS
• THE FIRST THREE QUANTUM NUMBERS CHARACTERIZE THE ORBITAL
WE SAY THAT THE ELECTRON “OCCUPIES” THIS
ORBITAL.
• THE SPIN QUANTUM NUMBER, MS, DESCRIBES THE SPIN
ORIENTATION OF AN ELECTRON.
59
 ELECTRON SPIN AND THE PAULI EXCLUSION
PRINCIPLE
• OTTO STERN AND WALTHER GERLACH FIRST OBSERVED ELECTRON SPIN MAGNETISM IN
1921. DIRECTED A BEAM OF SILVER ATOMS INTO THE FIELD OF A SPECIALLY DESIGNED
MAGNET. THE SAME EXPERIMENT CAN BE DONE WITH HYDROGEN ATOMS.
• THE BEAM OF HYDROGEN ATOMS IS SPLIT INTO TWO BECAUSE THE ELECTRON IN EACH
ATOM BEHAVES AS A TINY MAGNET WITH ONLY TWO POSSIBLE ORIENTATIONS. (SPIN
QUANTUM NUMBERS MS +1/2 AND MS -1/2.

60
ELECTRON CONFIGURATIONS AND ORBITAL
DIAGRAMS
• AN ELECTRON CONFIGURATION OF AN ATOM IS A PARTICULAR DISTRIBUTION
OF ELECTRONS AMONG AVAILABLE SUBSHELLS.
THE ELECTRON CONFIGURATION IS 1S22S22P1.
• THE NOTATION FOR A CONFIGURATION GIVES THE NUMBER OF ELECTRONS IN
EACH SUBSHELL, BUT WE USE A DIAGRAM TO SHOW HOW THE ORBITALS OF A
SUBSHELL ARE OCCUPIED BY ELECTRONS. IT IS CALLED AN ORBITAL DIAGRAM.

61
 PAULI EXCLUSION PRINCIPLE
• THE PAULI EXCLUSION PRINCIPLE, WHICH SUMMARIZES EXPERIMENTAL OBSERVATIONS,
STATES THAT NO TWO ELECTRONS IN AN ATOM CAN HAVE THE SAME FOUR
QUANTUM NUMBERS.
• IF ONE ELECTRON IN AN ATOM HAS THE QUANTUM NUMBERS N=1, L = 0, ML = 0,AND
MS =+1/2, NO OTHER ELECTRON CAN HAVE THESE SAME QUANTUM NUMBERS.
PAULI EXCLUSION PRINCIPLE: AN ORBITAL CAN HOLD AT MOST TWO ELECTRONS,
AND THEN
ONLY IF THE ELECTRONS HAVE OPPOSITE SPINS.

62
BUILDING-UP PRINCIPLE AND THE PERIODIC
TABLE
• THE CONFIGURATION ASSOCIATED WITH THE LOWEST ENERGY LEVEL OF THE
ATOM CORRESPONDS TO A QUANTUM MECHANICAL STATE CALLED THE
GROUND STATE.
• OTHER CONFIGURATIONS CORRESPOND TO EXCITED STATES, ASSOCIATED WITH
ENERGY LEVELS OTHER THAN THE LOWEST.
• FOR EXAMPLE, THE GROUND STATE OF THE SODIUM ATOM IS KNOWN FROM
EXPERIMENT TO HAVE THE ELECTRON CONFIGURATION 1S22S22P63S1. THE
ELECTRON CONFIGURATION 1S22S22P63P1 REPRESENTS AN EXCITED STATE OF
THE SODIUM ATOM.
63
64
 BUILDING-UP PRINCIPLE (AUFBAU
PRINCIPLE)
• MOST OF THE CONFIGURATIONS CAN BE EXPLAINED IN TERMS OF THE BUILDING-UP
PRINCIPLE (OR AUFBAU PRINCIPLE), A SCHEME USED TO REPRODUCE THE ELECTRON
CONFIGURATIONS OF THE GROUND STATES OF ATOMS BY SUCCESSIVELY FILLING
SUBSHELLS WITH ELECTRONS IN A SPECIFIC ORDER (THE BUILDING-UP ORDER).
FOLLOWING THIS PRINCIPLE, YOU OBTAIN THE ELECTRON CONFIGURATION OF AN
ATOM BY SUCCESSIVELY FILLING SUBSHELLS IN THE FOLLOWING ORDER:
1S, 2S, 2P, 3S, 3P, 4S, 3D, 4P, 5S, 4D, 5P, 6S, 4F, 5D, 6P, 7S, 5F

65
66
 ORBITAL DIAGRAMS OF ATOMS; HUND’S
RULE
• IN ABOUT 1927, FRIEDRICH HUND DISCOVERED AN EMPIRICAL RULE
DETERMINING THE LOWEST ENERGY
ARRANGEMENT OF ELECTRONS IN A SUBSHELL.
HUND’S RULE STATES THAT THE LOWEST-ENERGY ARRANGEMENT OF
ELECTRONS IN A SUBSHELL IS OBTAINED BY PUTTING ELECTRONS INTO
SEPARATE ORBITALS OF THE SUBSHELL WITH THE SAME SPIN BEFORE
PAIRING ELECTRONS.

67
68
PERIODIC TABLE OF ELEMENTS
 PERIODIC TABLE OF THE ELEMENTS
• IN 1869 THE RUSSIAN CHEMIST DMITRI MENDELEEV (1834–1907) AND
THE GERMAN CHEMIST J. LOTHAR MEYER (1830–1895), WORKING
INDEPENDENTLY, MADE SIMILAR DISCOVERIES.
• THEY FOUND THAT WHEN THEY ARRANGED THE ELEMENTS IN ORDER
OF ATOMIC MASS, THEY COULD PLACE THEM IN HORIZONTAL ROWS,
ONE ROW UNDER THE OTHER, SO THAT THE ELEMENTS IN EACH
VERTICAL COLUMN HAVE SIMILAR PROPERTIES.
A TABULAR ARRANGEMENT OF ELEMENTS IN ROWS AND COLUMNS,
HIGHLIGHTING THE REGULAR REPETITION OF PROPERTIES OF THE
ELEMENTS, IS CALLED A PERIODIC TABLE.
70
• A MODERN VERSION OF THE PERIODIC TABLE, WITH THE ELEMENTS
ARRANGED BY ATOMIC NUMBER.
• EACH ENTRY LISTS THE ATOMIC NUMBER, ATOMIC SYMBOL, AND ATOMIC
MASS OF AN ELEMENT.
• THE BASIC STRUCTURE:
• A PERIOD CONSISTS OF THE ELEMENTS IN ANY ONE HORIZONTAL ROW
OF THE PERIODIC TABLE.
• A GROUP CONSISTS OF THE ELEMENTS IN ANY ONE COLUMN OF THE
PERIODIC TABLE.
71
72
 METALS, NONMETALS, AND METALLOIDS
• A METAL IS A SUBSTANCE OR MIXTURE THAT HAS A CHARACTERISTIC LUSTER, OR
SHINE, AND IS GENERALLY A GOOD CONDUCTOR OF HEAT AND ELECTRICITY. EXCEPT
FOR MERCURY, THE METALLIC ELEMENTS ARE SOLIDS AT ROOM TEMPERATURE (ABOUT
20C).
• A NONMETAL IS AN ELEMENT THAT DOES NOT EXHIBIT THE CHARACTERISTICS OF A
METAL. MOST OF THE NONMETALS ARE GASES OR SOLIDS. THE SOLID NONMETALS
ARE USUALLY HARD, BRITTLE SUBSTANCES. BROMINE IS THE ONLY LIQUID NONMETAL.
• THESE ELEMENTS, SUCH AS SILICON (SI) AND GERMANIUM (GE), ARE USUALLY GOOD
SEMICONDUCTORS—ELEMENTS THAT, WHEN PURE, ARE POOR CONDUCTORS OF
ELECTRICITY AT ROOM TEMPERATURE BUT BECOME MODERATELY GOOD
73
CONDUCTORS AT HIGHER TEMPERATURES.
 ELECTRON CONFIGURATIONS AND THE
PERIODIC TABLE
• CONSIDER HELIUM, NEON, ARGON, AND KRYPTON, ELEMENTS IN GROUP VIIIA
OF THE PERIODIC TABLE. NEON, ARGON, AND KRYPTON HAVE
CONFIGURATIONS IN WHICH A P SUBSHELL HAS JUST FILLED. (HELIUM HAS A
FILLED 1S SUBSHELL; NO 1P SUBSHELL IS POSSIBLE.)

74
• AN ELECTRON IN AN ATOM OUTSIDE THE NOBLE-GAS OR PSEUDO-NOBLE-
GAS CORE IS CALLED A VALENCE ELECTRON.
• THE MAIN-GROUP ELEMENTS ALL HAVE VALENCE-SHELL CONFIGURATIONS
NSANPB, WITH SOME CHOICE OF A AND B.
• SIMILARLY, IN THE D-BLOCK TRANSITION ELEMENTS , A D SUBSHELL IS BEING
FILLED.
• IN THE F-BLOCK TRANSITION ELEMENTS (OR INNER TRANSITION ELEMENTS),
AN F SUBSHELL IS BEING FILLED.

75
76
 EXCEPTIONS TO THE BUILDING-UP
PRINCIPLE
• THERE ARE SOME EXCEPTIONS, HOWEVER, AND CHROMIUM (Z =24) IS THE FIRST WE
ENCOUNTER. THE BUILDING-UP PRINCIPLE PREDICTS THE CONFIGURATION [AR]3D44S2,
THOUGH THE CORRECT ONE IS FOUND EXPERIMENTALLY TO BE [AR]3D54S1.
• COPPER (Z 29) IS ANOTHER EXCEPTION TO THE BUILDING-UP PRINCIPLE, WHICH PREDICTS
THE CONFIGURATION [AR]3D94S2, ALTHOUGH EXPERIMENT SHOWS THE GROUND-STATE
CONFIGURATION TO BE [AR]3D104S1.

77
 WRITING ELECTRON CONFIGURATIONS
USING THE PERIODIC TABLE
• IN MANY CASES, YOU NEED ONLY THE CONFIGURATION OF THE OUTER
ELECTRONS.
• VALENCE-SHELL - NSANPB, WHERE N, THE PRINCIPAL QUANTUM NUMBER = PERIOD
NUMBER
• THE TOTAL NUMBER OF VALENCE ELECTRONS- A + B, CAN BE OBTAINED FROM THE
GROUP NUMBER.
• FOR EXAMPLE, GA VALENCE-SHELL CONFIGURATION 4S24P1 IS IN PERIOD 4, SO N
= 4. IT IS IN GROUP IIIA, SO THE NUMBER OF VALENCE ELECTRONS IS 3.
78
79
PERIODICITY OF THE ELEMENTS
 MENDELEEV’S PREDICTIONS FROM THE
PERIODIC TABLE
• ONE OF MENDELEEV’S PERIODIC TABLES IS, THOUGH SOMEWHAT DIFFERENT FROM MODERN
TABLES, IT SHOWS ESSENTIALLY THE SAME ARRANGEMENT.
• MENDELEEV LEFT SPACES IN HIS PERIODIC TABLE FOR WHAT HE FELT WERE UNDISCOVERED
ELEMENTS. THERE ARE BLANK SPACES IN HIS ROW 5—FOR EXAMPLE,
• BY WRITING THE KNOWN ELEMENTS IN THIS ROW WITH THEIR ATOMIC WEIGHTS, HE COULD
DETERMINE APPROXIMATE VALUES (BETWEEN THE KNOWN ONES) FOR THE MISSING ELEMENTS
(VALUES IN PARENTHESES).

81
82
 SOME PERIODIC PROPERTIES

• THE ELECTRON CONFIGURATIONS OF THE ATOMS DISPLAY A PERIODIC VARIATION WITH

INCREASING ATOMIC NUMBER (NUCLEAR CHARGE).
THE PERIODIC LAW STATES THAT WHEN THE ELEMENTS ARE ARRANGED BY ATOMIC NUMBER,
THEIR PHYSICAL AND CHEMICAL PROPERTIES VARY PERIODICALLY.
• WE WILL LOOK AT THREE PHYSICAL PROPERTIES OF AN ATOM:
• ATOMIC RADIUS,
• IONIZATION ENERGY,
• ELECTRON AFFINITY.
83
 ATOMIC RADIUS

• THE ATOMIC RADII ARE COVALENT RADII, WHICH ARE OBTAINED FROM MEASUREMENTS OF
DISTANCES BETWEEN THE NUCLEI OF ATOMS IN THE CHEMICAL BONDS OF MOLECULAR
SUBSTANCES.
• 1. WITHIN EACH PERIOD (HORIZONTAL ROW), THE ATOMIC RADIUS TENDS TO DECREASE WITH
INCREASING ATOMIC NUMBER (NUCLEAR CHARGE). THE LARGEST ATOM IN A PERIOD IS A
GROUP IA ATOM AND THE SMALLEST IS A NOBLE-GAS ATOM.
• 2. WITHIN EACH GROUP (VERTICAL COLUMN), THE ATOMIC RADIUS TENDS TO INCREASE WITH
THE PERIOD NUMBER.

84
85
 IONIZATION ENERGY
• THE FIRST IONIZATION ENERGY (OR FIRST IONIZATION POTENTIAL) OF AN ATOM IS
THE MINIMUM ENERGY NEEDED TO REMOVE THE HIGHEST-ENERGY (THAT IS, THE
OUTERMOST) ELECTRON FROM THE NEUTRAL ATOM IN THE GASEOUS STATE.

86
87
88
 ELECTRON AFFINITY
• THE ELECTRON AFFINITY IS THE ENERGY CHANGE FOR THE PROCESS OF ADDING AN
ELECTRON TO A NEUTRAL ATOM IN THE GASEOUS STATE TO FORM A NEGATIVE ION.

89
 PERIODICITY IN THE MAIN-GROUP
ELEMENTS
• HYDROGEN (1S1)
ALTHOUGH THE ELECTRON CONFIGURATION OF HYDROGEN
WOULD SEEM TO PLACE THE ELEMENT IN GROUP IA,
- ITS PROPERTIES ARE QUITE DIFFERENT, AND IT SEEMS BEST TO CONSIDER
THIS ELEMENT AS BELONGING IN A GROUP BY ITSELF.
- THE ELEMENT IS A COLORLESS GAS COMPOSED OF H2 MOLECULES.

90
91
 GROUP IA ELEMENTS, THE ALKALI METALS
(NS1)
• THE ALKALI METALS
• SOFT AND REACTIVE,
• REACTIVITY'S INCREASING- DOWN THE COLUMN OF ELEMENTS.
• ALL OF THE METALS REACT WITH WATER TO PRODUCE HYDROGEN.
• 2LI(S) + 2H2O(L) → 2LIOH(AQ) + H2(G)
• ALL OF THE ALKALI METALS FORM BASIC OXIDES WITH THE GENERAL
FORMULA R2O.
92
93
GROUP IIA ELEMENTS, THE ALKALINE EARTH
METALS (NS 2)
• THE ALKALINE EARTH METALS
• ARE ALSO CHEMICALLY REACTIVE BUT MUCH LESS SO THAN THE
ALKALI METALS.
• REACTIVITY'S INCREASE GOING DOWN THE GROUP.
• THE ALKALINE EARTH METALS FORM BASIC OXIDES WITH THE
GENERAL FORMULA RO.

94
95
 GROUP IIIA ELEMENTS (NS2NP1)

• THE FIRST GROUP IIIA ELEMENT, BORON, IS A METALLOID.

• OTHER ELEMENTS IN THIS GROUP—ALUMINUM, GALLIUM, INDIUM, AND THALLIUM—
• ARE METALS. (GALLIUM-IT MELTS READILY IN THE PALM OF THE HAND)
• THE OXIDES IN THIS GROUP HAVE THE GENERAL FORMULA R2O3.
• BORON OXIDE, B2O3, IS AN ACIDIC OXIDE; ALUMINUM OXIDE,
AL2O3, AND GALLIUM OXIDE, GA2O3, ARE AMPHOTERIC OXIDES.
• THE CHANGE IN THE OXIDES FROM ACIDIC TO AMPHOTERIC TO BASIC
IS INDICATIVE OF AN INCREASE IN METALLIC CHARACTER OF THE ELEMENTS.

96
97
 GROUP IVA ELEMENTS (NS 2NP 2)
• THIS BEGINS WITH THE NONMETAL CARBON, C,
• FOLLOWED BY THE METALLOIDS SILICON, SI, AND GERMANIUM, GE, AND THEN THE METALS TIN,
SN, AND LEAD, PB.
• ALL THE ELEMENTS IN THIS GROUP FORM OXIDES WITH THE GENERAL FORMULA RO2,
• CARBON DIOXIDE, CO2, AN ACIDIC OXIDE, IS A GAS.
• SILICON DIOXIDE, SIO2, AN ACIDIC OXIDE, EXISTS AS QUARTZ AND WHITE SAND.
• GERMANIUM DIOXIDE, GEO2, IS ACIDIC, THOUGH LESS SO THAN SILICON DIOXIDE.
• TIN DIOXIDE, SNO2, AN AMPHOTERIC OXIDE,
• LEAD DIOXIDE, PBO2, IS AMPHOTERIC. LEAD HAS A MORE STABLE MONOXIDE, PBO.
98
99
 GROUP VA ELEMENTS (NS 2NP 3)
• THE GROUP VA ELEMENTS- FROM NONMETAL (NITROGEN, N, AND PHOSPHORUS, P) TO METALLOID
(ARSENIC, AS, AND ANTIMONY, SB) TO METAL (BISMUTH, BI).
• NITROGEN OCCURS AS A COLORLESS, ODORLESS, RELATIVELY UNREACTIVE GAS WITH N2
MOLECULES;
• WHITE PHOSPHORUS IS A WHITE, WAXY SOLID WITH P4 MOLECULES.
• GRAY ARSENIC IS A BRITTLE SOLID WITH METALLIC LUSTER;
• ANTIMONY IS A BRITTLE SOLID WITH A SILVERY, METALLIC LUSTER.
• BISMUTH IS A HARD, LUSTROUS METAL WITH A PINKISH TINGE.
• THE GROUP VA ELEMENTS FORM OXIDES WITH EMPIRICAL FORMULAS R2O3 AND R2O5. IN SOME
CASES, THE MOLECULAR FORMULAS ARE TWICE THESE FORMULAS—THAT IS, R4O6 AND R4O10.
100
101
 GROUP VIA ELEMENTS, THE CHALCOGENS
(NS2NP 4)
• THESE ELEMENTS, THE CHALCOGENS
• NONMETAL (OXYGEN, O, SULFUR, S, AND SELENIUM, SE)
• TO METALLOID (TELLURIUM, TE)
• TO METAL (POLONIUM, PO).
• SULFUR, SELENIUM, AND TELLURIUM FORM OXIDES WITH THE FORMULAS RO2 AND RO3.
• TEO2, ARE ACIDIC; TEO2 IS AMPHOTERIC.
• POLONIUM HAS AN OXIDE POO2, WHICH IS AMPHOTERIC,

102
103
 GROUP VIIA ELEMENTS, THE HALOGENS (NS
2NP 5)
• THE HALOGENS ARE REACTIVE NONMETALS WITH THE GENERAL MOLECULAR FORMULA X2,
WHERE X SYMBOLIZES A HALOGEN.
• FLUORINE, F2, IS A PALE YELLOW GAS;
• CHLORINE, CL2, A PALE GREENISH YELLOW GAS;
• BROMINE, BR2, A REDDISH BROWN LIQUID;
• IODINE, I2, A BLUISH BLACK SOLID THAT HAS A VIOLET VAPOR
• LITTLE IS KNOWN ABOUT THE CHEMISTRY OF ASTATINE, AT, BECAUSE ALL ISOTOPES ARE
RADIOACTIVE WITH VERY SHORT HALF-LIVES. IT MIGHT BE EXPECTED TO BE A METALLOID.
• EACH HALOGEN FORMS SEVERAL COMPOUNDS WITH OXYGEN; THESE ARE GENERALLY
UNSTABLE, ACIDIC OXIDES. 104
105
 GROUP VIIIA ELEMENTS, THE NOBLE GASES
(NS 2NP 6)
• THE GROUP VIIIA ELEMENTS EXIST AS GASES CONSISTING OF UNCOMBINED
ATOMS.
• FOR A LONG TIME THESE ELEMENTS WERE THOUGHT TO BE CHEMICALLY INERT,
BECAUSE NO COMPOUNDS WERE KNOWN.
• THEN, IN THE EARLY 1960S, SEVERAL COMPOUNDS OF XENON WERE PREPARED.
• NOWCOMPOUNDS ARE ALSO KNOWN FOR ARGON, KRYPTON, AND RADON.
• THESE ELEMENTS ARE KNOWN AS THE NOBLE GASES BECAUSE OF THEIR RELATIVE
UNREACTIVITY. 106
107