There are multiple trends on the periodic table, but we are going to discuss four of the trends which are the following: atomic radius, electron affinity, electronegativity and ionization energy.

• Electron affinity is the change in energy of a neutral atom when an electron is added to the atom. The electron affinity of elements decreases from top to bottom in a group, and increases from left to right in a period.
• The atomic radius is essentially how large an atom is. The atomic radius of atoms increases from top to bottom in a group, and decreases from left to right in a period. Also, we can look at the atomic radius for ions as well. Cations are smaller than the neutral atom and anions are larger than the neutral atom.
• The electronegativity is how strongly an atom pulls electrons to itself. Think of electronegativity as "greediness." How "greedy" an atom is for electrons. For example, Fluorine is the most greedy element and Cesium is the least greedy element. The electronegativity of elements decreases from top to bottom in a group, and increases from left to right in a period.
• The ionization energy is the energy required to pull an electron away from an atom. The higher the ionization energy the more energy to pull an electron away from the atom. The ionization energy of elements decreases from top to bottom in a group, and increases from left to right in a period.

Watch the following video to learn more about these four trends:

https://youtu.be/G3qbooMh6Fc

Mirek2, CC0, via Wikimedia Commons