Periodicity

by increasing atomic (proton) number

• atomic radius increases • more inner shells so shielding increases • nuclear attraction on outer electrons decrease • first ionisation energy decreases

• nuclear charge increases • same shell: similar shielding • nuclear attraction increases • atomic radius decreases • first ionisation energy increases

• 2p sub-shell in boron has a more energy than 2s sub-shell in Beryllium • in boron 2p electron is easier to remove than one of the 2s electrons in beryllium • 1st I.E. of boron lower than 1st I.E of Beryllium

• highest energy electrons are in a 2p sub-shell • on O, paired electrons in one of the 2p orbitals repel one another, making it easier to remove an electron from an O atom than N • 1st I.E of oxygen is less than 1st I.E of N

• conduct electricity in solids and liquid states - delocalised electrons can move through the structure

• high melting and boiling points - large amount of energy needed to overcome the strong electrostatic attraction between the cations and electrons

• insoluble - electrostatic attraction is too strong

• high melting points and boiling points - large amounts of energy needed to overcome the strong covalent bond

• insoluble - far too strong to be broken by interaction with solvents

• insulators except graphene and graphite • in diamond and silicon, no free electrons • in graphene and graphite, there are free electrons available for conductivity

repeating trends in physical and chemical properties

removal of 1 mol of electrons from 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions

electrostatic attraction between cations and delocalised electrons