FC7 IONISATION ENERGIES & RADII

Question 1

atomic radius

Answer 1

the average distance between the nucleus and the outermost electron in an atom

Question 2

the average distance between the nucleus and the outermost electron in an atom

Answer 2

atomic radius

Question 3

nuclear charge

Answer 3

the charge of the nucleus due to the number of protons

Question 4

the charge of the nucleus due to the number of protons

Answer 4

nuclear charge

Question 5

shielding effect

Answer 5

caused by the repulsion between the inner shell electrons and the outer shell electrons. This reduces the attraction between the nucleus and outer electrons (outweighs nuclear charge)

Question 6

caused by the repulsion between the inner shell electrons and the outer shell electrons. This reduces the attraction between the nucleus and outer electrons (outweighs nuclear charge)

Answer 6

shielding effect

Question 7

first ionisation energy

Answer 7

energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous unipositive ions

Question 8

energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous unipositive ions

Answer 8

first ionisation energy

Question 9

Why is the first ionisation energy for B lower than Be?

Answer 9

the electron being removed from B is from a 2p subshell, which is at higher energy than the electron being removed from Be, which is in a 2s subshell ∴ less energy is needed to remove the outer electron from B than Be, as the outer electron of B is less attracted to its nucleus than for Be

Question 10

Why is the first ionisation energy for O less than N?

Answer 10

The electron being removed from O is a paired electron, which experiences mutual repulsion therefore less energy is required to remove it than the unpaired electron from N

Question 10

Define successive ionisation energies

Answer 10

The energies needed to remove each electron from an atom for one mole of gaseous atoms in succession

Question 10

The energies needed to remove each electron from an atom for one mole of gaseous atoms in succession

Answer 10

Successive ionisation energies

Question 11

What is the general trend for successive ionisation energies and why

Answer 11

Increase as the remaining electrons crowd closer to the nucleus after each ionisation. This is because there is less mutual repulsion between the remaining electrons. This leads to the attraction between the nucleus and outer electrons to increase so the ionic radius decreases therefore more energy is required for each successive ionisation

Question 12

What is the general trend in ionisation across a period

Answer 12

General trend increases because Atomic radius decreases because the nuclear charge increases across a period whereas the number of electron shells and shielding don’t change across a period therefore the attraction between the nucleus and outermost electrons increases therefore more energy is needed to remove the outer electron

Question 13

What is the general trend in ionisation down a group

Answer 13

General trend decreases because the atomic radius increases down a group because there is an increase in nuclear charge down a group and the number of electron shells increases. The greater shielding effect outweighs the greater nuclear charge down the group therefore the attraction between the nucleus and the outer electrons decreases therefore less energy is needed to remove the outer electron

Question 14

By how many times do successive I.E.s increase by within a shell and also from a shell closer to the nucleus

Answer 14

Within a shell = roughly doubles
From a shell closer to the nucleus = 8 to 10 times