1. Atomic Radius

The atomic radius decreases across a period from left to right due to the increasing nuclear charge. However, it increases down a group because of the addition of electron shells.

2. Ionization Energy

Ionization energy increases across a period as the attraction between the nucleus and electrons strengthens, requiring more energy to remove an electron. It decreases down a group due to increased atomic size.

3. Electronegativity

Electronegativity increases across a period as atoms attract electrons more strongly. It decreases down a group as the atomic size increases, reducing the nucleus' pull on bonding electrons.

4. Metallic and Non-Metallic Character

Metallic character decreases across a period and increases down a group. Non-metallic character shows the opposite trend, increasing across a period and decreasing down a group.

5. Reactivity

Reactivity in metals increases down a group, while for non-metals, it decreases. Across a period, reactivity in metals decreases, and in non-metals, it increases.