2.2 The Periodic Table
The Periodic Table
Every block represents an element
Every periodic table has a key
The Periodic Table
Where did the modern periodic table come
from?


Newlands
Mendeleyev
Modern Periodic Table
Period or Series – a horizontal row of
elements, numbered 1-7)
Group or Family – a vertical row of
elements (numbered 1-18 on the modern
table) (long ago: roman numerals)
Modern Periodic Table
Staircase – divides the metals from the
nonmetals
Metalloids – look like metals but act like
nonmetals
The Periodic Law
States that when elements are arranged in
order of increasing atomic mass, certain
physical and chemical characteristics
repeat in a regular pattern (periodically)
Modern Periodic Table
Atomic Mass – defined relative to the
mass of a carbon atom, which is given a
mass of 12 amu
AMU (atomic mass unit) – defined as 1/12
the mass of a carbon atom
Period / Group Names
Group 1 – Alkali Metals


Soft, silver colored metals that react violently
with water
React with the halogens
Group 2 – Alkaline Earth Metals

Light, reactive metals that form oxide coatings
with air exposure (ex MgO, CaO)
Period / Group Names
Group 17 – Halogens


Extremely reactive (F is the most)
Form hydrogen halides (ex HCl)
Group 18 – Noble Gases

Extremely low chemical reactivity
Period / Group Names
Transition Elements

Groups 3-12
Representative Elements

Groups 1-2, & 13-18
* Hydrogen is the exception to almost every
rule in chemistry
The Atom
The Atom
Is the smallest part of an element that is
still representative of that element
A neutral particle composed of a nucleus
(containing protons and neutrons) and
electrons
# electrons = # protons
Electrons
eA small, negatively charged subatomic
particle
Has negligible mass
Nucleus
The centre of an atom
Contains most of the mass and all of the
positive charge of an atom
Protons
p+
Positively charged subatomic particle
Found in the nucleus
Mass of 1 amu
Neutrons
n
Uncharged (neutral)
Found in the nucleus
Mass of 1 amu
Atomic Number and Atomic Mass
Atomic Number


The number of protons an atom has
Different for each element
Atomic Mass (Mass Number)

# protons + # neutrons