Which statement is true about the ionic size of the elements in a group as one moves from top to bottom in that group?

Ionic size does not vary in any predictable way within the group.

Ionic size increases from top to bottom within the group.

Ionic size decreases from top to bottom within the group.

Ionic size stays the same within the group.

Ionic size increases from top to bottom within the group.

Explanation:

Ions are formed when neutral atoms of elements gain or lose electron (s). The ionic radius is the distance from the nucleus of an ion to the outermost energy level. The ionic size or radius increases down the group as the number of energy level increases. Therefore, an ion of an element lower in the group will be larger than the ion of an element higher in the group. For example, an ion of potassium, K+, is larger in size compared to the ion of sodium, Na + since K + has more energy levels than Na+.

Option B = ionic sizes increases from top to bottom.

Explanation:

Definition of atomic radii:

The atomic radius is the distance between center of two bonded atoms.

Cation:

When an atom lose the electrons the formed is called cation.

e. g Na⁺ sodium lose one electron and form cation.

Anion:

when an atom gain the electrons the ions formed is called anion.

e. g N³⁻

Trend along period:

As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases. Same is the case with ions. Ionic size decreases moving from left to right.

Trend along group:

In group by addition of electron atomic radii increase from top to bottom due to increase in atomic number and addition of extra shell. The ionic size also increases from top to bottom.

If we compare the cationic and anionic size with neutral atomic radii, the anionic size is greater than neutral atomic radii because of addition of extra shell while cationic size is smaller because of removal of one electronic shell.