What are the four periodic trends mentioned in typical chemistry studies?

The four periodic trends that are commonly discussed in chemistry studies are electronegativity, ionization energy, atomic radius, and electron affinity.

Electronegativity refers to the tendency of an atom to attract electrons in a chemical bond. As you move across a period from left to right, electronegativity increases due to the increasing nuclear charge that attracts the bonding electrons more strongly. Conversely, as you move down a group, electronegativity decreases because the added electron shells reduce the nucleus's pull on bonding electrons.

Ionization energy is the energy required to remove an electron from an atom in the gas phase. This trend increases across a period due to the increasing effective nuclear charge and decreases down a group because of the increased distance of the outermost electrons from the nucleus, which makes them easier to remove.

The atomic radius is the size of an atom, which typically decreases across a period as electrons are added to the same shell while the nuclear charge increases, pulling the electrons closer to the nucleus. Conversely, the atomic radius increases down a group due to the addition of new electron shells, which outweighs the increased nuclear charge.

Electron affinity is the energy change that occurs when an electron is added to a neutral atom to form a negative ion