3.1.1 ionisation energy

Question 1

define first ionisation energy

Answer 1

enegry needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 2

explain how nuclear charge affects 1IE?

Answer 2

more protons = greater nuclear charge
= stronger attraction between outer electron and nucleus
INCREASES 1IE

Question 3

explain how atomic radius affects 1IE

Answer 3

larger atom = greater distance between outer e- and nucleus
weaker electrostatic attraction
DECREASES 1IE

Question 4

explain how electron shielding affects 1IE

Answer 4

more shells around an atom = more layers to block attraction between outer e- and nucleus
= outer e- more easily lost
DECREASES 1IE

Question 5

explain why 2IE is always higher than 1IE

Answer 5

energy required to remove an e from a positive ion is greater
more attraction

Question 6

describe the trends in 1IE on the periodic table

Answer 6

1IE increases across a period and decreases down a group

Question 7

explain why 1EI decreases down a group

Answer 7

shielding will increase = no. of shells increases
atomic radium increases = more shells between outer e- and nucleus
overpowers the higher nuclear charge from more protons
e- easier to lose

Question 8

explain why 1IE increases across a period

Answer 8

nuclear charge increase = more protons in nucleus
= greater attraction between e- and nucleus
same number of shells !!
= shielding same
atomic radius decreases = bigger nucleus but same no. of shells
= decreases distance between outer e
more difficult to lose e-

Question 9

explain the drop in 1IE between group 2 and 3

Answer 9

E.g&raquo_space; Mg and Al
new sub-shell is introduced
= more shielding
= greater atomic radius; further from nucleus
= easier to lose e-
Al has a SLIGHTLY LOWER 1IE than Mg

Question 10

explain the drop in 1IE between group 5 and 6

Answer 10

E.g&raquo_space; P and S
same atomic radius + shielding
P has 3 e- in 3p sub-shell = 1 in each orbital
S has 4 e- in 3p sub-shell = 1 orbital has 2 e- in it
= electrons experience repulsion in same orbital
= easier to lose e-
S has SLIGHTLY LOWER 1IE than P

Question 11

how do the trends in 1IE provide evidence for electronic structure

Answer 11

group 2 and 3 &raquo_space; evidence for sub-shells
group 5 and 6&raquo_space; evidence for orbitals

Question 12

what are successive ionisation energies?

Answer 12

each time you remove and e- from an atom there is a successive IE
generally successive IE increases in an atom
= difficult to remove e- from an increasingly +ive ion
= less repulsion against remaining e-

Question 13

how can you determine the group number from an IE graph

Answer 13

place of the first big jump = group number
= big jump is when a new shell is broken into
= requires lots of E due to stronger attraction + less shielding