Question

why are the trends and exceptions to the trends in ionization energy observed? check all that apply. ionization energy tends to increase down a group because the electrons get farther away from the nucleus. ionization energy tends to increase across a period because the nuclear charge increases. ionization energy tends to increase across a period because electrons are added to the same main energy level. the ionization energies of the elements in group 16 tend to be slightly smaller than the elements in group 15 because the fourth electron is added to an unfilled p - orbital. the ionization energies of elements in group 13 tend to be lower than the elements in group 2 because the full s orbital shields the electron in the p orbital from the nucleus.

Explanation:

1. Ionization energy decreases down a group as electrons are farther from the nucleus, so the first statement is false.
2. Across a period, nuclear charge increases, pulling electrons closer and increasing ionization energy. Also, electrons are added to the same main energy - level, making it harder to remove an electron, so the second and third statements are true.
3. In Group 15, the p - subshell is half - filled which is a stable configuration. In Group 16, the fourth electron in the p - subshell is added to an already occupied orbital, and the electron - electron repulsion makes it easier to remove an electron, so the fourth statement is true.
4. In Group 13, the filled s - orbital shields the electron in the p - orbital from the nucleus, making it easier to remove the p - electron compared to Group 2 elements, so the fifth statement is true.

Answer:

B. Ionization energy tends to increase across a period because the nuclear charge increases.
C. Ionization energy tends to increase across a period because electrons are added to the same main energy level.
D. The ionization energies of the elements in Group 16 tend to be slightly smaller than the elements in Group 15 because the fourth electron is added to an unfilled p orbital.
E. The ionization energies of elements in Group 13 tend to be lower than the elements in Group 2 because the full s orbital shields the electron in the p orbital from the nucleus.