Question

question 5 of 10
what trend does the first ionization energy follow, going down the periodic table?
a. the first ionization energy decreases because the outermost electron is farther from the nucleus.
b. the first ionization energy increases because there are more protons in the nucleus.
c. the first ionization energy increases because there are more electrons in the atom.
d. the first ionization energy decreases because atoms get smaller.

Explanation:

The first - ionization energy is the energy required to remove the outermost electron from a neutral atom in the gaseous state. Going down a group in the periodic table, the number of electron shells increases. The outermost electron is in a shell that is farther from the nucleus, and the effective nuclear charge experienced by this electron decreases due to shielding by inner - shell electrons. As a result, it is easier to remove the outermost electron, and the first - ionization energy decreases.

Answer:

A. The first ionization energy decreases because the outermost electron is farther from the nucleus.