can someone tell me a good way to remember and know the difference between atomic radius and ionization energy

Question

largest atomic radius in period 5?
largest atomic radius in group 3A
highest ionization energy in group 18
lowest ionization energy in period 2
configuration [Ar] 5s2 4d10 5p2

Answer 1

Assuming you mean the trends of radius and IE....

The way I do it is I know the atomic radius trends bigger down a group, smaller across a period.
Then you rationalize all other trends using atomic size. For ionization energy, the larger the atom, the easier it would be to sustain a charge. Atoms don't like to be charged, and the larger it is, the more volume to spread that charge over. So the bigger atoms will give up electrons more easily than small ones. Or you can think of small atoms as being desperate to hang onto electrons because they're so close to the nucleus.

Answer 2

The atomic radius is the distance between the nucleus and the outermost electron in an atom. The ionization energy is the energy require to remove one mole of electrons from a gaseous atom.

The largest atomic radius in period 5 is that of Xenon

The largest atomic radius in group 3a is that of probably Thallium.

The highest ionization energy in group i8 is that of RADON

Lowest ionization energy in period 2 is Sodium

CInfiguration is that of Germanium

Answer 3

When ionization energy increases, the outer electrons are nearer the nucleus, since you need more energy to extract an electron near the nucleus. So in one period the ionization energy increases from right to left and the atomic radius decreases

in period 5 largest atomic radius is Rb (rubidium)