Periodic Table of Elements

chlorine
nitrogen

gold
silver
mercury
oxygen hydrogen
helium
sodium niobium

neodymium
carbon
 Elements
 Science has come
along way since
Aristotle’s theory of
Air, Water, Fire, and
Earth.
 Scientists have
identified 90 naturally
occurring elements,
and created about 28
others.
Elements
 The elements,
alone or in
combinations,
make up our
bodies, our world,
our sun, and in
fact, the entire
universe.
The most abundant element in the
earth’s crust is oxygen.
 Periodic Table
 The periodic table organizes the elements in
a particular way. A great deal of information
about an element can be gathered from its
position in the period table.
 For example, you can predict with
reasonably good accuracy the physical and
chemical properties of the element. You can
also predict what other elements a particular
element will react with chemically.
 Understanding the organization and plan of
the periodic table will help you obtain basic
information about each of the 118 known
elements.
Key to the Periodic Table
 Elements are organized on
the table according to their
atomic number, usually
found near the top of the
square.
 The atomic number refers
to how many protons an
atom of that element has.
 For instance, hydrogen
has 1 proton, so it’s
atomic number is 1.
 The atomic number is
unique to that element.
No two elements have
the same atomic number.
 What’s in a square?
• Different periodic
tables can include
various bits of
information, but
usually:
• atomic number
• symbol
• atomic mass
• number of valence
electrons
• state of matter at room
temperature.
 Atomic Number
 This refers to how
many protons an
atom of that
element has.
 No two elements,
have the same
number of
Bohr Model of Hydrogen Atom protons.
Wave Model
 Atomic Mass
 Atomic Mass refers
to the “weight” of
the atom.
 It is derived at by
adding the number
of protons with the This is a helium atom. Its atomic
Hmass is 4 (protons plus
number of neutrons).

neutrons. What is its atomic number?

Atomic Mass and Isotopes
 While most atoms
have the same number
of protons and
neutrons, some don’t.
 Some atoms have
more or less neutrons
than protons. These
are called isotopes.
 An atomic mass
number with a decimal
is the total of the
number of protons plus
the average number of
neutrons.
Atomic Mass Unit (AMU)
 The unit of
measurement for
an atom is an
AMU. It stands for
atomic mass unit.
 One AMU is equal
to the mass of one
proton.
 Atomic Mass Unit (AMU)
 There are
6 X 1023 or
600,000,000,000,000,
000,000,000 amus in
one gram.
 (Remember that
electrons are 2000
times smaller than
one amu).
Symbols
 All elements have

C
their own unique
symbol.
Carbon  It can consist of a

Cu
single capital
letter, or a capital
letter and one or
Copper two lower case
letters.
Common Elements and
Symbols
 Valence Electrons
 The number of valence
electrons an atom has
may also appear in a
square.
 Valence electrons are
the electrons in the
outer energy level of
an atom.
 These are the
electrons that are
transferred or shared
when atoms bond
together.
 Properties of Metals
 Metals are good
conductors of heat and
electricity.
 Metals are shiny.
 Metals are ductile (can
be stretched into thin
wires).
 Metals are malleable
(can be pounded into
thin sheets).
 A chemical property of
metal is its reaction with
water which results in
corrosion.
Properties of Non-Metals
 Non-metals are poor
conductors of heat
and electricity.
 Non-metals are not
ductile or malleable.
 Solid non-metals are
brittle and break
easily.
 They are dull.
 Many non-metals are
gases.
Sulfur
Properties of Metalloids
 Metalloids (metal-like)
have properties of both
metals and non-metals.
 They are solids that can
be shiny or dull.
 They conduct heat and
electricity better than
non-metals but not as
well as metals.
 They are ductile and
Silicon malleable.
 Families Periods
 Columns of elements are  Each horizontal row of
called groups or families. elements is called a
 Elements in each family period.
have similar but not  The elements in a period
identical properties. are not alike in properties.
 For example, lithium (Li),  In fact, the properties
change greatly across
sodium (Na), potassium even given row.
(K), and other members of
 The first element in a
family IA are all soft, period is always an
white, shiny metals. extremely active solid. The
 All elements in a family last element in a period, is
have the same number of always an inactive gas.
valence electrons.
Hydrogen

 The hydrogen square sits atop Family

AI, but it is not a member of that family.
Hydrogen is in a class of its own.
 It’s a gas at room temperature.
 It has one proton and one electron in its
one and only energy level.
 Hydrogen only needs 2 electrons to fill
up its valence shell.
 Alkali Metals
 The alkali family is found in
the first column of the
periodic table.
 Atoms of the alkali metals
have a single electron in
their outermost level, in
other words, 1 valence
electron.
 They are shiny, have the
consistency of clay, and are
easily cut with a knife.
Alkali Metals
 They are the most
reactive metals.
 They react violently
with water.
 Alkali metals are
never found as free
elements in nature.
They are always
bonded with
another element.
What does it mean to be
reactive?
 We will be describing elements according to their
reactivity.
 Elements that are reactive bond easily with other
elements to make compounds.
 Some elements are only found in nature bonded
with other elements.
 What makes an element reactive?
 An incomplete valence electron level.
 All atoms (except hydrogen) want to have 8 electrons in
their very outermost energy level (This is called the rule of
octet.)
 Atoms bond until this level is complete. Atoms with few
valence electrons lose them during bonding. Atoms with 6,
7, or 8 valence electrons gain electrons during bonding.
5
Alkaline Earth Metals

 They are never found uncombined in nature.

 They have two valence electrons.
 Alkaline earth metals include magnesium
and calcium, among others.
Transition Metals
 Transition Elements
include those elements
in the B families.
 These are the metals
you are probably most
familiar: copper, tin,
zinc, iron, nickel, gold,
and silver.
 They are good
conductors of heat and
electricity.
Transition Metals

 The compounds of transition metals are usually

brightly colored and are often used to color paints.
 Transition elements have 1 or 2 valence electrons,
which they lose when they form bonds with other
atoms. Some transition elements can lose electrons
in their next-to-outermost level.
Transition Elements

 Transition elements have properties

similar to one another and to other
metals, but their properties do not fit in
with those of any other family.
 Many transition metals combine
chemically with oxygen to form
compounds called oxides.
 Boron Family
 The Boron Family is
named after the first
element in the family.
 Atoms in this family have 3
valence electrons.
 This family includes a
metalloid (boron), and the
rest are metals.
 This family includes the
most abundant metal in the
earth’s crust (aluminum).
 Carbon Family
 Atoms of this family have
4 valence electrons.
 This family includes a
non-metal (carbon),
metalloids, and metals.
 The element carbon is
called the “basis of life.”
There is an entire branch
of chemistry devoted to
carbon compounds called
organic chemistry.
 Nitrogen Family
 The nitrogen family is named
after the element that makes
up 78% of our atmosphere.
 This family includes non-
metals, metalloids, and
metals.
 Atoms in the nitrogen family
have 5 valence electrons.
They tend to share electrons
when they bond.
 Other elements in this family
are phosphorus, arsenic,
antimony, and bismuth.
 Oxygen Family
 Atoms of this family have 6
valence electrons.
 Most elements in this family
share electrons when
forming compounds.
 Oxygen is the most
abundant element in the
earth’s crust. It is extremely
active and combines with
almost all elements.
 Halogen Family
 The elements in this
family are fluorine,
chlorine, bromine,
iodine, and astatine.
 Halogens have 7
valence electrons, which
explains why they are Halogen atoms only need
the most active non- to gain 1 electron to fill their
metals. They are never outermost energy level.
found free in nature. They react with alkali
metals to form salts.
Noble Gases

 Noble Gases are colorless gases that are extremely un-

reactive.
 One important property of the noble gases is their inactivity.
They are inactive because their outermost energy level is full.
 Because they do not readily combine with other elements to
form compounds, the noble gases are called inert.
 The family of noble gases includes helium, neon, argon,
krypton, xenon, and radon.
 All the noble gases are found in small amounts in the earth's
atmosphere.
Rare Earth Elements
 The thirty rare earth
elements are composed
of the lanthanide and
actinide series.
 One element of the
lanthanide series and
most of the elements in
the actinide series are
called trans-uranium,
which means synthetic or
man-made.
 Mendeleev
 In 1869, Dmitri Ivanovitch
Mendeléev created the first accepted
version of the periodic table.
 He grouped elements according to
their atomic mass, and as he did, he
found that the families had similar
chemical properties.
 Blank spaces were left open to add
the new elements he predicted
would occur.
Matter

 All matter is composed of atoms and groups

of atoms bonded together, called molecules.
 Substances that are made from one type of
atom only are called pure substances.
 Substances that are made from more than one
type of atom bonded together are called
compounds.
 Compounds that are combined physically, but
not chemically, are called mixtures.
 Elements, Compounds,
Mixtures

 Sodium is an element.
 Chlorine is an
element.
 When sodium and
chlorine bond they
make the compound
sodium chloride,
Compounds have different properties
commonly known as than the elements that make them up.
table salt.
Table salt has different properties than
sodium, an explosive metal, and chlorine,
a poisonous gas.
 Elements, Compounds,
Mixtures
 Hydrogen is an element.
 Oxygen is an element.
 When hydrogen and
oxygen bond they make
the compound water.
 When salt and water are
combined, a mixture is
created. Compounds in
mixtures retain their
individual properties.
The ocean is
a mixture.
Elements, compounds, and
mixtures

 Mixtures can be separated by physical

means.
 Compounds can only be separated by
chemical means.
 Elements are pure substances. When the
subatomic particles of an element are
separated from its atom, it no longer retains
the properties of that element.
Periodic Trends

 The first and most important is atomic

radius.
 Radius is the distance from the center
of the nucleus to the “edge” of the
electron cloud.
 Atomic Radius

 Since a cloud’s edge is difficult to define,

scientists use a defined covalent radius, or
half the distance between the nuclei of 2
bonded atoms.
 Atomic radii are usually measured in
picometers (pm = 1 x 10-9 m) or angstroms
(Å). An angstrom is 1 x 10-10 m.
Example of covalent radius

 Two Br atoms bonded together are

2.86 angstroms apart.
 2.86 Å

 Arad = 2.86 Å = 1.43 Å


2
 Atomic Radius

 The trend for atomic radius in a

FAMILY/GROUP (vertical column) is to go
from smaller at the top to larger at the bottom
of the family.
 Why?
 With each step down the family, we add an
entirely new PEL to the electron cloud,
making the atoms larger with each step.
 Atomic Radius

• What happens to atomic structure as we step

from left to right?

• Each step adds a proton and an electron

(and 1 or 2 neutrons).

• The effect is that the more positive nucleus

has a greater pull on the electron cloud.
 Atomic Radius

 Group Trend – As you go down a column,

atomic radius increases
As you go down, e- are filled into orbitals that
are farther away from the nucleus (attraction
not as strong)
 Periodic Trend – As you go across a period
(L to R), atomic radius decreases
As you go L to R, e- are put into the same
orbital, but more p+ and e- total (more
attraction = smaller size)
 Overall Trend of Atomic Radius
TOWARD BOTTOM LEFT

DECREASES TOWARD TOP RIGHT

INCREASES
 Ionic Radius

 Ionic Radius –
size of an atom
when it is an ion
 Ionic Radius

Metals – lose e-, which means more p+

than e- (more attraction) SO…
Cation Radius < Neutral Atomic Radius
Nonmetals – gain e-, which means more e-
than p+ (not as much attraction) SO…
Anion Radius > Neutral Atomic Radius
 Ionic Radius

 Group Trend – As you go down a column,

ionic radius increases
 Periodic Trend – As you go across a period (L
to R), cation radius decreases,
anion radius decreases, too.
As you go L to R, cations have more attraction
(smaller size because more p+ than e-). The
anions have a larger size than the cations, but
also decrease L to R because of less
attraction (more e- than p+)
Ionic Radius
 Ionization Energy

• Once an electron has been removed from

one atom and added to another, both
atoms are changed.
• These atoms have been “ionized”.
• The number of protons and electrons is no
longer equal.
 Ionization Energy

 Group Trend – As you go down a column,

ionization energy decreases
As you go down, atomic size is increasing (less
attraction), so easier to remove an e-
 Periodic Trend – As you go across a period (L to
R), ionization energy increases
As you go L to R, atomic size is decreasing (more
attraction), so more difficult to remove an e-
(also, metals want to lose e-, but nonmetals do
not)
 Ionization Energy

DECREASES
DOWNWARD
TOP TO
BOTTOM
 Electron Affinity

 What does the word ‘affinity’ mean?

 Electron affinity is the energy change that
occurs when an atom gains an electron
(also measured in kJ).
 Where ionization energy is always
endothermic, electron affinity is usually
exothermic, but not always.
 Electron Affinity

 Electron affinity is exothermic if there is an

empty or partially empty orbital for an
electron to occupy.
 If there are no empty spaces, a new orbital
or PEL must be created, making the
process endothermic.
 This is true for the alkaline earth metals
and the noble gases.
Electronegativity

 Electronegativity is a measure of an
atom’s attraction for another atom’s
electrons.
 It is an arbitrary scale that ranges from
0 to 4.
 The units of electronegativity are
Paulings.
Electronegativity

 Group Trend – As you go down a column,

electronegativity decreases
As you go down, atomic size is increasing, so
less attraction to its own e- and other atom’s
e-
 Periodic Trend – As you go across a period
(L to R), electronegativity increases
As you go L to R, atomic size is decreasing, so
there is more attraction to its own e- and
other atom’s e-
The Octet Rule

 The “goal” of most atoms (except H, Li

and Be) is to have an octet or group of
8 electrons in their valence energy
level.
 They may accomplish this by either
giving electrons away or taking them.
The Octet Rule

 Metals generally give electrons,

nonmetals take them from other
atoms.
 Atoms that have gained or lost
electrons are called ions.
Ions

 When an atom gains an electron, it

becomes negatively charged (more
electrons than protons ) and is called
an anion.
 In the same way that nonmetal atoms
can gain electrons, metal atoms can
lose electrons.
 They become positively charged
cations.
 Ions
 Here is a simple way to remember
which is the cation and which the
anion:

+ +

This is Ann Ion. This is a cat-ion.

She’sunhappy and
He’s a “plussy” cat!
negative.
Ionic Radius

 Cations are always smaller than the

original atom.
 The entire outer PEL is removed
during ionization.
 Conversely, anions are always larger
than the original atom.
 Electrons are added to the outer PEL.
 1. What is the unit for atomic radius?
 2. Ions that is positively charged.
 3. When an atom gains an electron, it
becomes negatively charged, it is called?
 4. Which of the two has greater atomic
radius, Nitrogen or Antimony?
 5. Which of the following elements has
greater electronegativity: Boron, Carbon,
Nitrogen, Oxygen Fluorine and Neon?
 6. Which of the following elements has
greater electronegativity: Boron, Aluminum,
Galium, Indium and Thalium?
 7. Which of the following has greater ionic
radius: Be, Mg, Ca, Sr, Ba, Ra?
 8. What elements is the most abundant in
Earth’s crust?
 9. What elements is the most abundant in
Earth’s atmosphere?
10-14. Give 5 elements that belongs to metals.
15-17. Give 3 elements that belongs to
metalloids.
18-20. Name 3 noble gases.