The Periodic Table

• The periodic table is a list of all the known elements arranged in Groups and Periods

• All the elements on the LHS are metals – RHS are non – metals.

• A Group is a vertical column.• A Period is a row.

Groups• The elements in the same group have

similar chemical properties.• Group Names• Group 1 - Alkali metals – very reactive

metals – stored in Oil. • Group 7 – Halogens – very reactive non –

metals.• Group 8 – The Noble Gases – very unreactive

non-metal gases.• Transition metals – lie between groups 2 and

3.

Elements

• Elements are made up of only one type of atom.

• Atoms are made up of tiny sub-atomic particles:

• Protons, Electrons and Neutrons.• The atom is in two parts a Core in the

middle – The Nucleus, and the Electron Clouds which orbit the Nucleus.

The Structure of the Atom

The Nucleus contains Protons and Neutrons.Electrons are found in the Electron clouds.Protons: Mass =1 a.m.u, charge +Electrons: Mass=1/1850 a.m.u,

charge-Neutrons:Mass 1 a.m.u, charge 0.

Properties of Elements

• Every element has a unique number called Atomic Number.

• The Atomic Number is the number of Protons ( this is equal to the number of electrons in a neutral atom)

• The Mass Number is a total of the particles with mass i.e. protons and neutrons.

Calculations!• Number of Protons = Atomic Number.• Number of Electrons= Number of protons.• Number of neutrons = Mass number – Atomic

Number• Example• Chlorine – Mass No. = 35, Atomic No. = 17• Number protons= 17, Number of electrons =

17, Number of Neutrons = 35-17 = 18.

Electrons

• Electrons are arranged inside the electron clouds. These are inside “Energy Levels”

• The first energy level holds a maximum of 2 electrons within 1 cloud.

• The second energy level can hold up to 8 electrons – in pairs in 4 clouds

• The third energy level also hols 8 electrons in 4 clouds.

Electron Arrangement• This is the name given to how the

electrons are organised.• Example • Sodium has 11 electrons. 2 will be in the

first energy level, 8 in the second energy level and the one remaining electron will be in the third energy level.

• The electron arrangement for Sodium is written as 2,8,1.

Isotopes

• These are atoms of the same elements that have different mass numbers i.e. different numbers of neutrons.

• Example• Chlorine – has 2 isotopes – one has

a mass of 35 a.m.u. the other has a mass of 37 a.m.u.

Relative Atomic Mass( R.A.M. )• This is the average mass of the isotopes

– taking into consideration their abundance. It is usually not a whole number.

• Example• Chlorine has a R.A.M. of 35.5• It has 2 isotopes one with a mass of 35

the other has a mass of 37.• Therefore there must be more of the 35

isotope.