Atomic size increases down a group. The increasing trend occurs because as you go down a group more energy levels cause the atom to be larger. Shielding also affects the size; the electrons in lower energy levels cause less pull to those electrons outside of it.

Down a group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital. This results in a larger atomic radius.

Trend-wise, as one moves from left to right across a period in the modern periodic table, the ionization energy increases as the nuclear charge increases and the atomic size decreases. The decrease in the atomic size results in a more potent force of attraction between the electrons and the nucleus.

Periodic Trends: Electronegativity, Ionization Energy, Atomic Radius - TUTOR HOTLINE.

Major trends are electronegativity, ionization energy, electron affinity, atomic radius, and metallic character. The existence of these trends is due to the similarity in atomic structure of the elements in their group families or periods and because of the periodic nature of elements.

There are four main periodic trends: electronegativity, atomic size, ionization energy, and electron affinity.