first ionisation energies

Question 1

periodicity

Answer 1

repeating pattern of physical or chemical properties going across the periods

Question 2

why is helium the largest first ionisation energy?

Answer 2

it’s electron is in the first shell closest to the nucleus and has no shielding effects from inner shells. Helium has a bigger first ionisation energy than H as it has one more proton

Question 3

why do first ionisation energies decrease down a group?

Answer 3

as one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded so the attraction of the nucleus becomes smaller.

Question 4

why is there a general increase in first ionisation energy across a period?

Answer 4

as one goes across a period, the number of protons increases, making the effective attraction of the nucleus greater. the electrons are being added to the same shell which has the same shielding effect and the electrons are pulled in closer to the nucleus

Question 5

why has Na a much lower first ionisation energy than neon?

Answer 5

this is because Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. So Na’s outer electrin in easier to remove and has a lower ionisation energy

Question 6

why is there a small drop from Mg to Al?

Answer 6

Al is starting to fill a 3p sub shell whereas Mg has its outer electrons in the 3s sub shell. the electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons

Question 7

why is there a small drop from P to S?

Answer 7

with sulfur, there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital. when the second electron is added to a 3p orbital there is a slight repulsion between the 2 negatively charged electrons which makes the second electron easier to remove