trends in 1st ionisation energy across period 3

Question 1

why does the 1st ionisation energy of magnesium increase?

Answer 1

the first ionisation energy of magnesium increases due to the nuclear charge increasing but nuclear shielding stays constant

Question 2

why is the 1st ionisation energy of aluminium lower than the 1st ionisation energy of magnesium

Answer 2

the first ionisation energy of aluminium is lower than then magnesium because the electron being removed is 3p which is slightly further away from the nucleus therefore it has a slightly weaker electrostatic force of attraction

Question 3

why is the 1st ionisation energy of sulfur lower than phosphorus

Answer 3

the first ionisation energy of sulfur is lower than phosphorus because it is the first paired electron to be removed. Therefore there is repulsions between electrons in the orbital

Question 4

explain the trend in 1st ionisation energy going down a group

Answer 4

• going down a group the electron shielding increases
• this means the outer electron shell is further from the nucleus
• the electrostatic attraction between the nucleus and outer electron is weaker and therefore it is easier to remove an electron

Question 5

why do subsequent ionisation energies increase?

Answer 5

Subsequent ionisation energies increase because the electron being
removed is from an increasingly positively charged ion. There is a stronger
electrostatic attraction between the ion and the electron being removed
which means it requires more energy to remove

Question 6

why is there a big jump between 2nd and 3rd ionisation energy? (talk about the electrostatic attration)

Answer 6

There is a big jump between 2nd and 3rd ionisation energy because the
electron being removed is from a lower electron shell which is closer to the
nucleus with less electron shielding. The electrostatic attraction is greater
therefore requires more energy to remove

Question 7

what is the general trend in ionisation energy across period 3

Answer 7

ionisation energy increases as the shielding is constant but nuclear charge and proton number is increasing so there is a stronger electrostatic force of attraction between nucleus and outer electron so the outer electron is pulled closer to nucleus so atomic radii decreases