Periodicity

• Periodicity is a repeating trend in physical and chemical properties.
• S block elements have their highest energy electrons in the s orbital, p blocks in their p orbitals, d block in their d orbitals.
• Group 1 elements are called alkali metals, group 2 are called alkali earth metals. Group 3-12 are the transition metals. Group 15 are pnictogens, group 16 are chalcogens. Group 17 are called halogens and group 18 are noble gases.
• 1st ionisation energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of +1 ions. (Na -> [Na]^+ e-)
• Big jumps in the ionisation energy chart show transition to the next shell.
• Factors affecting ionisation energy: nuclear charge- more protons give a more positively charged nucleus therefore stronger attraction towards their e-.

  Atomic radius- the further away the outer electrons are from the nucleus, the weaker the attraction so can be removed easier.

  Shielding- inner shells repel outer ones, reducing the attraction between the e- and nucleus.
• Down the group, the 1st I.E decreases as although nuclear charge increases, the shielding increases as well as atomic radius, overcoming the larger charge.
• Across a period, I.E. increases as nuclear charge increases, atomic radius decreases and shielding stays the same.
• Seen in period 2 as well.

  A) S-orbital to p-orbital

  B) Paired e- in p-orbital

  
• Lithium and Be are giant metallic and C is giant covalent. N, O, F and Ne are diatomic and simple covalent.

  Na, Mg and Al are giant metallic, and Si is giant covalent, P4, S8, Cl2, and Ar are simple molecular.