1.1 - Periodicity

Periodicity

Higher Chemistry 1.1

The Periodic Table is arranged in order of increasing atomic number and elements are organised into groups and periods

Groups go down and elements in the same group have the same number of outer electrons

Periods go across and elements in the same period have the same number of occupied energy levels. 

The covalent radius is a measure of atomic size. It is defined as half the distance between the nuclei of two covalently bonded atoms.

As you go across a period, the atomic size decreases. This is because the nuclear charge increases. As it increases, the number of protons is also increasing. An increased nuclear charge results in the electrons being more strongly attracted to the nucleus making the size of the atom smaller

As you go down a group, the atomic size increases. This is because the number of energy levels is increased. Each layer of electrons shields the outer electrons from the nucleus so the outer electrons are less strongly attracted to the nucleus making the size of the atom larger 

The ionisation enthalpy is the energy required  to remove one mole of electrons from one mole of atoms in the …