Trends in the Periodic Table PDF

Trends in the Periodic Table The atomic radius of an element is half the distance between the nuclei of two atoms of the element joined together by a single covalent bond. Trends in atomic radius – Across a period: Atomic radius decreases due to: 1. Increased nuclear charge 2. The same screening e e...

Trends in the Periodic Table The atomic radius of an element is half the distance between the nuclei of two atoms of the element joined together by a single covalent bond. Trends in atomic radius – Across a period: Atomic radius decreases due to: 1. Increased nuclear charge 2. The same screening e ect Down a group: Atomic radius increases due to: 1. Extra energy levels 2. Increased screening 3. These o set an increase in nuclear charge Electronegativity – Across a period: Electronegativity increases due to: 1. Increase in nuclear charge 2. Smaller atomic radius Down a group: Electronegativity decreases due to: 1. Increase in atomic radius 2. Increased screening e ect 3. These are more important than an increased nuclear charge The 1st ionisation energy of an element is the minimum amount of energy required to remove the most loosely bound electron from 1 mole of gaseous atoms in their ground state. X(g) – e-  X+(g) Trends in 1st Ionisation energy – Across a period: 1st ionisation energy increases due to: 1. Increased nuclear charge 2. Decreased atomic radius Down a group: 1st ionisation energy decreases due to: 1. Increased atomic radius 2. Increased screening The 2nd ionisation energy of an element is the minimum amount of energy required to remove the most loosely bound electron from each singly charged positive ion in a mole of these ions. X+ (g) – e-  X2+(g) Atomic Radius: Going across a period: decreases 1)nuclear charge increases 2)energy levels stays the same =>more protons ->more pull ->pulls in closer Going down a group: increases 1)number of energy levels increase 2)screening e ect increases =>more shells+ same amount of protons = lessening pull Ionisation Energy: Going across a period: increases 1)nuclear charge increases 2)atomic radius decreases =>outer electrons closer to nucleus =harder to remove (Exceptions: Group II> III + Group V