Group 7(17), the halogens

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Question 20

Medium

The graph below shows the variation in first ionisation energy across the Period 3 elements (atomic numbers 11 to 18).

First ionisation energy across Period 3

Which statement correctly explains one of the marked features, $W$ , $X$ , $Y$ , or $Z$ ?

The first ionisation energy of $X$ is lower than that of $W$ because the outer electron in $X$ is removed from a $3p3\text{p}$ sub-shell, which is of higher energy than the $3s3\text{s}$ sub-shell of $W$ and is shielded by it.

The first ionisation energy of $Z$ is lower than that of $Y$ because the outer electron in $Z$ is removed from a $3p3\text{p}$ orbital that experiences significantly greater shielding from inner shells.

The atomic radius of $W$ is smaller than that of $X$ because $X$ has a higher nuclear charge, drawing the outer electrons closer to the nucleus.

The first ionisation energy of $Z$ is lower than that of $Y$ because the paired electrons in the $3s3\text{s}$ orbital of $Z$ experience spin-pair repulsion.

Group 7(17), the halogens

Question 20

Group 7(17), the halogens Questions

Group 7(17), the halogens

Question 20

Group 7(17), the halogens Questions