Periodic Trends

Question 1

Electronegativity

Answer 1

Describes an atom’s ability to compete for electrons with other atoms to which it is bonded. At atomic property. EN = IE - EA

Question 2

Electronegativity: General Trend

Answer 2

increases from left to right across a period. decreases from top to bottom.

Question 3

Electronegativity: Exceptions

Answer 3

For groups 13 + 14, the electronegativity value starts to increase going down the group after period 2 (starting at period 3). Boron not bigger than Gallium but Carbon bigger than Germanium.
Not an exception but Hydrogen has EN = 2.1 (same as Phosphourous and less than Carbon (2.5))

Question 4

Electron Affinity

Answer 4

the enthalpy change that occurs when an atom in the gas phase gains an electron. The more negative the EA, the more attraction the atom has for the electron.

Question 5

Electron Affinity: General Trend

Answer 5

From left to right across a period the EA becomes more negative. EA becomes less negative from top to bottom.

Question 6

Electron Affinity: Exceptions

Answer 6

For Group 1: Electron Affinity is most negative for Hydrogen. For Groups 13-17: EA is the most negative for period 3 atoms. EA becomes progressively less negative as you head down the periods from there. EA is more negative for period 4 than period 2 with the exception of Fluorine and Carbon.
Groups 2, Nitrogen, and 18 all have positive or very small negative electron affinities.
Groups 13 and 15: Group 13 atoms are less negative than group 1 atoms of the same period. Group 15 atoms are less negative than group 14 atoms of the same period.

Question 7

Ionisation Energy

Answer 7

The quantity of energy a gaseous atom must absorb to be able to expel an electron.

Question 8

Ionisation Energy: General Trends

Answer 8

ionisation energy increases from left to right across a period. Ionisation energy decreases from top to bottom along a group.

Question 9

Ionisation Energy: Exceptions

Answer 9

Group 2 has greater ionisation energy than group 13. Group 15 has greater ionisation energy than group 16.

Question 10

Atomic Radius

Answer 10

The distance from the nucleus within which 95% of the electron charge density is found.

Question 11

Atomic Radius: General Trends

Answer 11

Atomic radius decreases from left to right through a period and increases from top to bottom through a group.

Question 12

Atomic Radius: Exceptions

Answer 12

Noble gases are not known well. Transition metals are skewed

Question 13

Ionic Radius

Answer 13

The radius of atomic ions

Question 14

Cations: General Trends

Answer 14

Cations are smaller than the atom. For isoelectronic cations, the more positively charged cation will be the smaller cation.

Question 15

Anions: General Trends

Answer 15

Anions are larger than the atom. For isoelectronic anions, the larger the magnitude of the negative charge the larger the anion.

Question 16

Ionic Radius: Exceptions

Answer 16

No noble gase ions.
Transition metals are difficult.
When comparing with noble gases use isoelectronic rules.