Using Electron Shells to Explain Group Trends Flashcards

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What is an electron shell?

An electron shell is a level around the nucleus where electrons move. Electrons fill the lowest shell first.

For the main groups, the group number is the same as the number of electrons in the outer shell.

They have the same number of electrons in their outer shell, so they form ions and react in similar ways.

Atoms of Group 1 elements gain an extra electron shell each step down the group, so they get larger.

Their outer electron is in a shell further from the nucleus and is more shielded, so it is lost more easily, making them more reactive.

Atoms of Group 7 elements also gain extra electron shells as you go down, so their outer shell is further from the nucleus.

Their outer shell is further from the nucleus and more shielded, so it is harder to attract and gain an extra electron, making them less reactive.

Electron shielding is when inner shells of electrons block some of the attraction between the nucleus and the outer-shell electrons.

They have full outer electron shells, so they do not need to gain or lose electrons and so hardly react.

Atoms lower down Group 0 have more electron shells and more electrons, so the forces between their atoms are stronger, giving higher boiling points.