Periodicity

Periodicity

Repeating trend of physical or chemical properties

Atomic radius increases down a group as:

• There is an extra energy levels

• More shielding

• Attraction to the nucleus decreases

Atomic radius decreases across a period as:

• Number of protons increases

• Same energy level

• Same shielding

• Attraction to the nucleus increases

First ionisation energy

The energy required to remove 1 mol of electrons from 1 mol of gaseous atoms

• X (g) → X⁺ (g) + e^-

Ionisation energies across Group 2

Trends in IE’s down the groups

• Extra energy level

• More shielding

• Attraction to the nucleus decrease

• Requires less energy to remove an electron

Trends in IE’s across the periods

• Number of protons increase

• Same energy level

• Same shielding

• Attraction to the nucleus increases

• Requires more energy to remove electrons

Deviations across the period: Group 3 Al>Mg

• Ionisation energy decreases

• Electron is removed form the higher energy p sub level

• Weaker attraction between the nucleus and outer electron

Deviation across the period: Group 3 S>P

• Ionisation energy decreases

• Mutual Repulsion

• Paired P orbital

Successive ionisation energies will always increase as:

• The positive charge on the ion increases

• Ionic radius decreases

• Nuclear attraction on the outer electron increases

Metallic Bonding

Strong electrostatic attraction between oppositely charged ions and a sea of delocalised electrons

Metallic bonding diagram

What factors affect the strength of the metallic bond?

• Ionic charge of the metal

• Smaller atomic radius

• Number of delocalised electrons

Properties of metals: Good conductors of heat and electricity

• The delocalised electrons are free to move

Properties of metals: High melting and Boiling points

• They have a strong electrostatic attraction between positive ions and delocalised electrons

Properties of metals: Malleable and ductile

• Layers of ions can slide over each other

Comparing melting and boiling points of substances

Name the structure of the substance

e.g. Giant ionic, Giant metallic, Giant Covalent, Simple molecular

• Name the type of bonding within the molecules

  e.g. Ionic, metallic, Covalent, IMF’s

• Compare melting points - amount of electrons, stronger forces presen