Periodic trends identify relationships between atomic structure and characteristics and their position on the periodic table. Below are several periodic trends and a short explanation of each:
1. Atomic radii
Atomic radii increase as one moves down a group. This is because additional energy levels are being added.
Atomic radii decrease as one moves to the right of a period. This is because additional protons are being added, making the nucleus more positive. This added positive charge within the nucleus pulls the electrons inward more- decreasing the size of the atomic radii.
2. Electronegativity and ionization energy
Electronegativity is the affinity an atom has for electrons. Ionization energy is the amount of energy needed to remove an electron from the outermost orbital from a neutral atom in the gas phase.
Both ionization energy and electronegativity increase as one moves to the right of the periodic table. This is also because additional protons are being added, making the nucleus more positive. The added positive charge results in the electrons being pulled and held on tighter by the nucleus. Thus, they are harder to remove. It also results in the atom having a greater pull for additional electrons.
Both ionization energy and electronegativity increase as one moves up a group. This is because there are less orbitals, so the electrons are closer to the positive nucleus. Thus, the atom has a greater pull for more electrons. The electrons that are present are held on more tightly.