Periodic Table
• Dmitri Mendeleev-recognized that
elements had repeating patterns (periodic)
and organized elements into a table by
increasing atomic mass
• With table he was able to predict that there
would be elements still unidentified by the
gaps in his table

• Protons = Atomic number
• Electrons = protons
• Neutrons = mass number (rounded)
minus the protons
• Protons do not change in an atom
• neutrons can change (isotopes)
• electrons can be shared or transferred
(when bonds are made)

• Henry Moseley - determined that the
number of protons - atomic number (which
is unique to each element) would allow the
elements to fit into very specific pattern
• All elements follow the Periodic Law –
chemical and physical properties change
periodically with atomic number

Metals
• Most elements are metals
• Found to the left of the zigzag line
(exception: hydrogen)
• Solid at room temp (exception: mercury)
Properties:
– Shiny
– Ductile
– Malleable
– Good conductors

Metalloids
• Also called semiconductors
• Border the zigzag line (exception Al)
• Have properties of both metals and
nonmetals depending on the conditions
• properties: depending on conditions
– Brittle
– Good conductors
– Some shiny (others dull)

nonmetals
• More than half are gases at room temp
• To the right of the zigzag line
• Properties:
– Not malleable or ductile
– Not shiny or dull
– Poor conductors

Each square on table
• Each square includes:
• Atomic number (protons)
• chemical symbol (color coded to identify
if element is a solid, liquid or gas at room
temp)
• element’s name
• Atomic mass (weighed average of isotopes)
• Background color (identifies metals,
nonmetals and metalloids on table)

• First letter of chemical symbol is always upper
case and any additional letters are lower case
• Rows (left to right) are called periods
• Rows-determines the number of energy
levels – 7 rows on the table
• Properties gradually change moving left to right
across each row from reactive (group 1) to non-
reactive (group 18)

Energy Levels
• 1st energy level – 2 valence electrons (max)
• 2nd energy level – 8 valence electrons (max)
• 3rd energy level – 18 valence electrons (max)
• And so on….
• Each energy level can have less valence
electrons but they can not have more than
the maximum valence electrons.

Energy Levels

• Columns (up and down) are called groups or
family
• Elements in the same group or family have
similar properties moving up and down each
column
• Each element in a family has the same number
of valence electrons in the last energy level
• Group number determine the valence electrons

Bonds
• To form bonds, elements must reach a full
state of 8 valence electrons in the last
energy level (octet rule)
• (Exception: Helium - would be first energy
level which is full at 2)

Group or Family Names
• Group 1 – Alkali Metals
• Group 2 – Alkaline Earth Metals
• Group 3-12 – Transition Metals
• Group 13 – Boron Group
• Group 14 – Carbon Group
• Group 15- Nitrogen Group
• Group 16 – Oxygen Group
• Group 17 – Halogens
• Group 18 – Noble Gases

Lanthanides and Actinides
(Rare earth metals)
• In periods 6 and 7 and appear at the
bottom of the periodic table to keep table
from being too wide
• Lanthanides are shiny reactive metals
• Actinides are unstable radioactive
• All elements after Pu-94 (plutonium) are
man-made in labs and don’t occur in
nature

Group 14-Carbon group
• Carbon forms organic compounds (all
living things contain carbon), makes more
compounds than any other element

Group 17-Halogens
• Valence 7 - has violent reactions with
alkali-metals (group 1) to form salt
compounds
– Highly reactive with other elements
– Do not appear in nature alone only in
compounds

Group 18-Noble Gases
• Valence 8 valence (full level)
• except helium which has 2 valence
electrons, which makes helium full
• very unreactive – inert
• Do not form compounds

Hydrogen
• Valence 1 electron in last energy level so it
is set above the alkali metals
• Properties: even though above metal
category, has properties of nonmetals
• Most abundant element in universe,
makes up stars