PERIODIC TABLE

KEY TO THE PERIODIC TABLE

• Elements are organized on the table ATOMIC MASS AND ISOTOPES

according to their atomic number,
• While most atoms have the same
usually found near the top of the
number of protons and neutrons, some
square
don’t
• The atomic number refers to how many
• Some atoms have more or fewer
protons an atom of that element has
neutrons than protons. These are called
• For instance, hydrogen has 1 proton, so
ISOTOPES
its atomic number is 1
• An atomic mass number with a decimal
• The atomic number is unique to that
is the total of the number of protons
element. No two elements have the
plus the average number of neutrons
same atomic number
ATOMIC MASS UNIT (AMU)
WHAT’S IN A SQUARE
• The unit of measurement for an atom is
• Different periodic tables can include
an AMU. It stands for atomic mass unit
various bits of information, but usually:
• One AMU is equal to the mass of one
1. Atomic Number
proton
2. Symbol
3. Atomic Mass SYMBOLS
4. Number of valence electrons
5. State of matter at room • All atoms have their own unique symbol
temperature • It consists of a capital letter and one or
two lower letters
ATOMIC NUMBER

• This refers to how many protons an

atom of that element has
• No two elements, have the same
number of protons

ATOMIC MASS

• Atomic Mass refers to the “weight” of

the atom
• It is derived by adding the number of
protons with the number of protons
VALENCE ELECTRONS • Elements in the periodic table are also grouped
into families, which are the columns. Elements
• The number of valence electrons an
in families have similar properties
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 METAL

• Metals are good conductors of heat and

electricity
• Metals are shiny
• Metals are ductile (can be stretched
• The elements are also categorized into periods
into thin wires)
or horizontal rows. Elements in periods do not
• Metals are malleable (can be pounded
have similar properties
into thin sheets)
• A chemical property of metal is its
reaction with water which results in
corrosion

PROPERTIES OF NON-METAL

• Non-metals are poor conductors of heat

and electricity
• Non-Metals are not ductile or malleable
• Solid non-metals are brittle or break
easily
• They are dull
• Many non-metals are gases

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 malleable
HYDROGEN or 8 valence electrons gain electrons
• The hydrogen square sits a top Family during bonding
AI, but it is not a member of that family.
ALKALINE EARTH METALS
Hydrogen is in a class of its own
• It’s a gas at room temperature • They are never found uncombined in
• It has one proton and one electron in its nature
one and only energy level • They have two valence electrons
• Hydrogen only needs 2 electrons to fill • Alkaline earth metals include
up its valence shell magnesium and calcium among
others
ALKALI METALS
TRANSITION METALS
• The alkali family is found in the first
column of the periodic table • Transition Elements include those
• Atoms of the alkali metals have a single elements in the B families
electron in their outmost level, in other • These are the metals you are probably
words, 1 valence electron most familiar with: copper, tin, zinc,
• They are shiny, have the consistency of iron, nickel, gold, and silver
clay, and are easily cut with a knife • They are good conductors of heat and
• They are the most reactive metals electricity
• They react violently with water • The compounds of transition metals are
• Alkali metals are never found as free usually brightly colored and often used
elements in nature. They are always to color paints
bonded with another element • Transition Elements have 1 or 2 valence
electrons, which they lose when they
WHAT DOES IT MEAN TO BE REACTIVE
form bonds with other atoms. Some
• We will be describing elements transition elements can lose electrons
according to their reactivity in their next-to-outermost level
• Elements that are reactive bond easily • Transition elements have properties
with other elements to make similar to one another and to other
compounds. metals, but their properties do not fit in
• Some elements are only found in nature with those of any other family
bonded with other elements • Many transition metals combine
chemically with oxygen to form
WHAT MAKES AN ELEMENT REACTIVE compounds called oxides
• 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,
BORON FAMILY HALOGENS

• The Boron Family is named after the • The elements in this family are fluorine,
first element in the family chlorine, bromine, iodine, and astatine
• Atoms in this family have 3 valence • Halogens have 7 valence electrons
electrons which explains why they are the most
• This family includes a metalloid (boron), active non-metals. They are never
and the rest are metals found free in nature
• This family includes the most abundant • Halogen atoms only need to gain 1
metal in the earth’s crust (aluminum) electron to fill their outermost energy
level
NITROGEN FAMILY
• They react with alkali metals to form
• The nitrogen family is named after the salts
element that makes up 78% of our
NOBLE GASES
atmosphere
• This family includes non-metals, • Noble Gases are colorless gases that are
metalloids, and metals extremely un-reactive
• Atoms in the nitrogen family have 5 • One important property of the noble
valence electrons. They tend to share gases is their inactivity. They are
electrons when they bond inactive because their outermost
• Other elements in this family are energy level is full
phosphorus, arsenic, antimony, and • Because they do not readily combine
bismuth with other elements to form
compounds, the noble gases are called
OXYGEN
inert
• Atoms of this family have 6 valence • The family of noble gases includes
electrons helium, neon, argon, krypton, xenon,
• Most elements in this family share and radon
electrons when forming compounds • All the noble gases are found in small
• Oxygen is the most abundant element amounts in the earth’s atmosphere
in the earth’s crust. It is extremely RARE EARTH ELEMENTS
active and combines with almost all
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
DMITRI IVANOVITCH MENDELEEV • We write SO2, not O2S

• In 1869, Mendeleev created the first POLYATOMIC IONS

accepted version of the periodic table
• Many of these groups of atoms have a
• He grouped elements according to their
charge associated with them and are
atomic mass, and as he did, he found
called polyatomic ions
that the families had similar chemical
• To determine the total number of each
properties
type of atom in a compound containing
• Blank spaces were left open to add the
a group within parentheses, multiply
new elements he predicted would occur
the subscript outside the parentheses
CHEMICAL FORMULAS by the subscript for each atom inside
the parentheses
• A chemical formula indicates the
elements present in a compound and TYPES OF CHEMICAL FORMULA
the relative number of atoms of each
• For example, H2O is the chemical EMPIRICAL FORMULA
formula to water; it indicates that water
• gives the relative number of atoms of
consists of hydrogen and oxygen atoms
each element in a compound
in a 2:1 ratio
• The formula contains the symbol for MOLECULAR FORMULA
each element accompanied by a
• gives the actual number of atoms of
subscript indicating the number of
atoms of that element. By convention, a each element in a molecule of the
subscript 1 is omitted compound
• The subscripts in a chemical formula are STRUCTURAL FORMULA
part of the compound’s definition – if
they change, the formula no longer • uses lines to represent chemical bonds
specifies the same compound and shows how the atoms in a molecule
• Chemical Formula list the most metallic are connected to each other
elements first
• The formula for Table Salt is NaCl, not • For hydrogen peroxide
ClNa • Molecular Formula: H2O2
• In compounds that do not include a • Empirical Formula: HO
metal, the more metal-like element is • The molecular formula is always a
listed first. whole-number multiple of the empirical
• Among non-metals, those to the left in formula
the periodic table are more metal-like • For many compounds, such as H2O, the
than those to the right and are normally molecular formula is the same as the
listed first. empirical formula
• We write NO2 and NO, not O2N and ON • Molecular models: three-dimensional
• Within a single column in the periodic representations of molecules that are
table, elements toward the bottom are used to represent compounds
more metal-like than elements toward • We use two types of molecular models:
the top Ball-and-stick and Space-filling
 • In Space-Filling models, atoms fill the • Molecular compounds are compounds
space between each other to more formed from two or more non-metals
closely represent our best idea for how
a molecule might appear if we could
scale it to a visible size

• Ionic compounds contain one or more

cation paired with one or more anion
• In most cases, the cations are metals,
and the anions are non-metals

IDENTIFYING SUBSTANCES

• Atomic Elements:
1. Elements that occur as single atoms
2. Monoatomic
3. Most elements
• Molecular Elements
1. Elements that occur in pairs
2. Diatomic
3. Seven elements

• When a metal combines with a

nonmetal, one or more electrons
transfer from the metal to the non-
metal, creating positive and negative
ions that are attracted to each other
• A compound composed of a metal and a
nonmetal is considered ionic