Topic 3: Periodicity – Trends in the Frist Ionisation Energies

Perhaps the most important part of the periodicity topic is the the trends and patterns in first ionisation energies both down a group and across a period. This is found under section 3.2.2 and 3.2.3 of the syllabus.

It builds on the ideas we covered yesterday – namely, the electron arrangement in the atom, as well as shielding of the outer electrons by the inner shells, the distance of the outer electrons from the nucleus and the number of protons in the nucleus. It is therefore improtant that your students are secure in these ideas.

When teaching about ionisation energies, ensure that you emphasize that it is an atom (Cl) and not a molecule (Cl₂) and also that the atom is in the gaseous state (Mg_(g) NOT Mg_(s)) – if students are asked to write equations showing ionisation they must use the state symbols.

The following youtube video is pretty good to help consolidate your teaching. I wouldn’t use it initially, but would use it to summarize everything. Good luck and enjoy!

[youtube]8F9nA4Fg3Rw[/youtube]