Question

1. what is the primary reason for the increase in ionization energy across a period? increase in atomic size decrease in electron shielding increase in number of protons both increase in number of protons and decrease in shielding

Explanation:

As you move across a period in the periodic table, the number of protons in the nucleus increases. This leads to a greater effective nuclear charge, which holds the electrons more tightly, making it more difficult to remove an electron and thus increasing ionization energy. Shielding remains relatively constant across a period, and atomic size decreases across a period rather than increasing.

Answer:

C. Increase in number of protons