Chemguide: Support for CIE A level Chemistry

Learning outcome 23: Chemical energetics

23.1: Lattice energy and Born-Haber cycles

Learning outcome 23.1.2

Before you go on, find and read this statement in your syllabus.

You will find almost all that you will need on the Chemguide page Electron affinity.

There are only numbers for the group trends for Group 17 (old Group 7), but statement 23.1.2(c) also wants Group 16 (old Group 6). They are:

O-140 kJ mol-1
S-200 kJ mol-1
Se-195 kJ mol-1
Te-190 kJ mol-1

The pattern is exactly the same as in Group 17 - a general fall with the first element being out of line. The reasons are the same as you have already read.

The syllabus only mentions first electron affinity. You will, however, need to know about second electron affinity as well for statements 23.1.3 and 23.1.4.

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© Jim Clark 2020