ionisation energy

Question 1

What does it mean if an atom is ionised?

Answer 1

when it loses one or more electrons to form a positive ion

Question 2

What is 1st ionisation energy?

Answer 2

the energy needed to remove one electron from each atom in a mole of gaseous atoms of an element

Question 3

What is the ionisation energy units ?

Answer 3

KJmol-1

Question 4

How would you write the first and second ionisation energy as an equation?

Answer 4

X (g) –> X+1 (g) + e-

2nd:
X+ (g) —> X+2 (g) + e-

Question 5

What are the 3 factors that affect ionisation energy?

Answer 5

nuclear charge
atomic radius
sheilding

Question 6

How does nuclear charge affect ionisation energy?

Answer 6

the stronger the positive nuclear charge, the more strongly the electrons will be attracted so the higher the ionisation energy with all other factors being equal

Question 7

How does atomic radius affect ionisation energy?

Answer 7

the increases distance the decreases attraction to the nucleus so a lower ionisation energy

Question 8

Why does atomic radius depend what shell the outer electrons are in?

Answer 8

the higher the shell, the higher the average distance from the nucleus

Question 9

Why does atomic radius depend on outer electrons being in the same shell?

Answer 9

the distance is still not equall due to different nuclear charges felt by the electrons so the higher to nuclear charge, the smaller the atomic radius

Question 10

How does sheilding affect ionisation energy?

Answer 10

makes the electron being sheilded easier to remove
the higher the shell the greater extent of sheilding
with other things being equal, the attraction to the nucleus will be weaker ans the ionisation energy will be lower

Question 11

What is sheilding?

Answer 11

an electron being removed is repelled by other electrons in the inner shells
the higher the shell the outer electron is in, the greater the no of inner shells so the greater the extent of sheilding

Question 12

What happens to ionisation energy across a period?

Answer 12

increases across a period because of decreasing atomic radius

Question 13

What is periodicity?

Answer 13

an approximately repeating trend across each period

Question 14

What happens to ionisation energy down a group?

Answer 14

decreases because:
- extra shell = further from the nucleus
- atomic radius increases
- outer electrons experiences more sheilding
- these effects outweigh the increasing nuclear charge so the outer electron is less attracted to the nucleus

Question 15

Where are the two places where the down a group trend that IE decreases does not apply?

Answer 15

between group 2 and 3 elements
between group 5 and 6 elements

Question 16

Why does ionisation energy decrease between group 2 and 3?

Answer 16

the highest energy electron is in the p-subshell for the g3 element but in the s-subshell for the g2 element
the p-subshell is slighty higher energy so it is slightly easier to remove the outer electron from the g3 element

Question 17

Why does ionisation energy decrease between group 5 and 6?

Answer 17

the highest energy electron is in a paired subshell for g6 but not in g5 element
repulsion between paired electrons raises their energy so it makes them slightly easier to remove from g6

Question 18

Why is the 2nd ionisation energy higher than the first?

Answer 18

once 1 electron has been removed, there are fewer electrons left so they repel each other and the remaining electrons are more attracted to the nucleus

Question 19

Why is there a big change in ionisation energies of the same element?

Answer 19

happens after a shell has been emptied so the next electron to be removed is closer to the nucleus and harder to remove

Question 20

How do you log Ionisation energies on your calculator?

Answer 20

shift, squared, log (insert no)

Question 21

Why would you need to log ionisation no.s?

Answer 21

they are too large and spread out to plot for graphs and to compare data