electron configuration and ionisation energies

define first ionisation energy (2 marks)

the energy required to remove one mole of electrons from one mole of gaseous atoms

to form 1 mole of gaseous +1 ions

give the equation for first ionisation

X (g) → X+ (g) + e-

give the definitions for third ionisation energy

the energy required to remove one mole of electrons from one mole of gaseous 2+ ions

to form 1 mole of gaseous +3 ions

give the equation for third ionisation

X+2 (g) → X+3 (g) + e-

give the electron configuration of chromium

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵

stability for having a half filled 3d orbital

give the electron configuration of copper

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰

stability for having a full 3d orbital

which are the 2 exceptions in electron config?

• chromium

• copper

what phrase should you use to answer exam questions on explaining trends in ionisation energies?

Never-number of protons and nuclear charge

Stop- shielding and shells

Dancing-distance from nucleus- atomic or ionic radius

Around- nuclear attraction

Earth- energy

explain the general trend in first ionisation energy across period 3

across period 3

the number of protons increases

shielding stays the same

so the attraction between the nucleus and the outermost electrons increases

so the atomic radius decreases

so more energy is needed to remove an electron

so the first IE increases

give the electron configuration of Sc 2+

1s² 2s² 2p⁶ 3s² 3p⁶

give the electron configuration of Mn 2+

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵

Model answer for explaining trends in ionisation energies

the nuclear charge (increases/decreases)

shielding (increases/decreases/stays the same)

the distance between the nucleus and outermost electrons (increases/decreases)

nuclear attraction for the outermost electrons (increases/decreases)

the energy needed to remove an electron (increases/decreases)

compare the first ionisation energies of period 2 and 3

period 3 has a lower first ionisation energies than period 2

because shielding increases, which out weighs the increase in nuclear charge

therefore there is an increase in distance between the nucleus and outermost electrons

therefore nuclear attraction decreases

and the energy to remove one electron decreases

give the model answer for describe and explain the changes in first IE across a period

1. general trend NSDAE

2. 1st dip

3. 2nd dip (due to repulsion in an orbital or subshell due to each of them having different energies)

order the subshells from highest to lowest energy

f > d > p > s

describe and explain the changes in first IE across period 2 (7 marks)

the nuclear charge increases

shielding stays the same

the distance between the nucleus and outermost electrons decreases

nuclear attraction for the outermost electrons increases

the energy needed to remove an electron increases

from Be to B there is a decrease due to the P subshell having higher energy than the S subshell

from N to O there is a decrease due to repulsion due to the occupied P orbital

which of these have a higher 2nd IE? and explain why

Na+ Mg+ Al+

Na+ because the electron in the 2p subshell which is a higher energy subshell

therefore requires more energy to remove

an element in period 3 has the following succesive first IE

1681, 3374, 6050, 8408, 11203, 15164, 17868, 92038, 106434

identify which element and explain why (2 marks)

there is a large increase in energy from the 7th and 8th IE

therefore must have 7 electrons in it’s outershell

so must be chlorine

sketch a graph for the first 5 Ionisation energies of Na