Question

Objective Knowledge Check Question 15 Re-order each list in the table below, if necessary, so that the atoms or ions in it are listed in order of decreasing size. atoms or ions in order atoms or ions of decreasing size Al, Mg. AI Mg. Al Al 1,F,C1 1.1.F 0.0.0 I Don't Know

can someone explain the one im missing and double check the ones i already did plz

Answer 1

An anion ( example I- ) has more electrons than in its neutral atom but it has same number of protons. So electrons feel a weak force of attraction from nucleus , also there is electrostatic repulsion between electrons . These factors results in increased atomic radii of anion.

While a cation (Al+2) has less electrons than in its neutral atom but number of protons are same . So force of attraction between nucleus and electrons is more which result in decreased atomic radii or size of cation.

Atoms or ions in order of decreasing size:

Mg > Al > Al+3

Across the period atomic size decreases, due to increase in nuclear charge.

I-​​​​​​ > Cl- > F-

Down the group, atomic size increases due to addition of shells

I- > I > Xe

Across the period, size decreases so 'I' is bigger in size than Xe. Anion size is always bigger than its neutral atom.