2. THE PERIODIC TABLE
CLASSIFYING THE ELEMENTS
In the periodic table:
• The elements are arranged in order of increasing proton number
• The vertical columns of elements with similar properties are called groups
• The horizontal rows are called periods
Distinction in the table
METALS NON-METALS
Most of elements Fewer than metals
Particular type of bonding Much wider range of
properties
They are divided by a line
6. GROUPS AND PERIODS IN THE PERIODIC TABLE
MAIN-GROUP ELEMENTS TRANSITION ELEMENTS NOBLE GASES
• Elements present in
group I to VIII
• These vertical
groups have similar
chemical and
physical properties
• Elements present
between groups II
and III
• The first row occurs in
period 4
• Elements present
in group VIII
• The least reactive
elemets
Group I : alkali metals, the most reactive metals
Group VII : halogens next to noble gases
In centre of the table there are the most unreactive elements
7. GROUP I: THE ALKALI METALS
• They are soft solids with low melting point and low
densities.
• They are highly reactive
• They have a silvery surface
• The physical properties change as we go down the
group
• They react VIGOROUSLY with WATER to produce:
quickly tarnishes
Became dull
Increases as we go down
the group
melting points become lower
density increases
HYDROGEN ALKALINE SOLUTION
8. GROUP VII: THE HALOGENS
• The most reactive non-metals
• Their reactivity decreses down the group
• They are all poisonous
• They all form diatomic molecules
• They all have a valency of 1
• Their compounds with hydrogen are usually strong acids
when dissolved in water
• Each of them produces a series of compounds with other
elements
• They can react directly with metals to form salts
• They all form negative ions carrying a single charge
9. GROUP VIII: THE NOBLE GASES
• A whole group of elements remain to be discovered
• They are present in Earth’s atmosphere
• They are particulary unreactive
• They were refered to as the inert gases
• Their melting points and boiling points are extremely low
• The electron arrangements of atoms are very stable
• They are between the two most reactive groups of elements (groups I and
VII)
So they don’t react readily with other atoms
The group VII elements gain or share electrons and the group I
elements lose electrons to reach a noble gas electron
arragement
10. WHAT IS ELECTRON CONFIGURATION?
An electron configuration is a shorthand
description of how electrons are arranged around
of an atom.
They are important because they help us predict
chemical behavior:
We can predict if two elements:
• will react or not
• what kind of reaction we are likely to have
• how strong the reaction will be
11. • Every element on the periodic table
consists of atoms, composed of protons,
neutrons and electrons (electrons exhibit
a negative charge and are found around
the nucleus of the atom in electron
orbitals).
• The four different types of orbitals (s, p,
d, f) have different shapes, and one
orbital can hold a maximum of two
electrons.
The p, d, f orbitals have different
sublevels, thus can hold more electrons.
12. The Electron Configuration of
each element is unique to its
position on the periodic table.
The energy level is determined
by the period (from 1 to 7) and
the number of electrons is given
by the atomic number.
Orbitals on different energy levels
are similar to each other, but they
occupy different areas in space.
