atomic structure - 1.6 electron arrangements and ionisation energy

Question 1

define ionisation energy

Answer 1

ionisation energy is the energy required to remove 1 mole of electrons from a mole of atoms in the gaseous state (kJ mol-1)

Question 2

in the 1st ionisation energy, why does the electron that is removed require the least amount of energy

Answer 2

because it is being removed from a neutral atom

Question 3

define first ionisation energy

Answer 3

the energy required to remove 1 mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 4

explain the trends in ionisation energy across a period

and explain exceptions (group 2 to 3 dip) + (group 5 to 6 dip)

Answer 4

across a period, ionisation energy increases
-nuclear charge increases so the attraction between nucleus and outer electron is very strong and therefore it requires more energy to remove electron

aluminium has a lower IE than magnesium
-Al outer electron is in 3p orbital
-Mg outer electron is in 3s orbital
-electron in the p orbital is of higher energy so requires more energy to remove it

sulfur has a lower IE than phosphorus
-S has a pair of electrons in 3p orbital, they will repel so require less energy to remove
-P has electrons in 3p orbital which are unpaired

in both cases, which go against the expected trend, are evidence that confirms the existence of s and p sub levels

Question 5

explain the trends in ionisation energy down a group

Answer 5

ionisation energy decreases down a group
-nuclear charge increases, however due to shielding (which increases down a group), there is less energy required to remove electron
-atomic radius increases
-weaker attraction between nucleus and outer electrons