The Structure of Atoms
• Neutrons = neutral
• Protons = positive charge
• Electrons = negative charge
• At the centre of an atom.
• Made up of protons and neutrons.
• Neutrons are heavier than protons – both are
much heavier than electrons.
• Atomic Number = Number of Protons
• Electrons spin around the nucleus. They don't
stay in defined areas around the nucleus. They
are found in clouds that can have different
• Electrons are negative and attracted to the
• The number of electrons and protons is the
• The electrons spin around the nucleus in
• The closer the shell is to the nucleus the
greater the attraction.
• Closer shells have lower energy levels and the
outermost shells the highest energy level.
Maximum number of electrons = 2n2
Shell Max. Number of Electrons
n = 1 2
n = 2 8
n = 3 18
n = 4 32
• Atoms that are joined = molecules or large
• These atoms are held together by chemical
Group 18 of the periodic table are the noble
gases – they are extremely stable and rarely
bond with other atoms.
• All other atoms react, gain, lose or share
electrons – result is a bond.
• The result is particles with full outer shells
that hold eight electrons.
• Ions are atoms that have become charged
because they have had electrons removed –
or because they have removed electrons
from other atoms.
• No longer neutral.
• Positively charged ions (+) have more protons
– lose electrons.
• Negatively charged ions (-) have more
electrons – gain electrons.
• Metal atoms only have a weak hold on their
• The outer-shell electrons can move
throughout the metal without being bound to
any one atom.
• Each metal atom becomes a positively
Opposite charges attract and the electrostatic
force provides bonding between the positive
ions and the loose electrons surrounding them.
• When metallic elements bond with non-metallic
• Metal atoms – weak hold on outer-shell
• Non-metallic atoms – strong hold on outer-shell
• Non-metallic tend to remove outer-shell
electrons from any metal atoms they are near.
• Electrostatic forces pull the +ve and –ve ions
together to form a strong ionic bond.
• Result in a three-dimensional structure called
• When non-metallic atoms bond with each
• Non-metals can’t remove electrons from other
• They share some of their outer-shell electrons
and form covalent bonds.
Non-metals only share enough electrons to fill
their outer-shell or have eight electrons in their
Group 1 and 2 – Alkali Metals and
Alkali metals form +1 ions, are too reactive to be
found naturally in pure form, have typical metal
properties, display similar chemical behaviour,
react violently with water producing an alkaline
solution and hydrogen gas.
Alkaline Earth metals all react in a similar way –
just slightly less reactive.
These elements display a wide range of
– non-metal carbon
– metalloids silicon and germanium
– metallic tin and lead
Group 17 – the Halogens
• Atoms form ions with a charge of -1.
• Are not found in nature in pure form – found
• Get bigger and less reactive as you move
down the group.
• All form molecules of two atoms.
• Have coloured and poisonous vapours.
Group 18 – the Noble Gases
• Occur naturally in the atmosphere.
• Incredibly stable and only react under extreme
• Groups 3-12
• Many of the most useful, colourful and
• All tend to be relatively hard with high melting