Question

1. which periodic trend refers to the energy required to remove an electron from an atom?

atomic radius
electron affinity
ionization energy
electronegativity

Explanation:

Ionization energy is defined as the energy required to remove an electron from an atom. Electron affinity is the energy change when an electron is added to a neutral atom. Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond. Atomic radius is the distance from the nucleus to the outermost shell of an atom.

Answer:

Ionization energy