Question

1. which of the following best explains why atomic radius decreases across a period? a) electron shielding increases b) number of protons increases, pulling electrons in c) more energy levels are added d) atoms gain electrons and repel each other 10. what happens to ionization energy as you move down a group? a) it increases b) it decreases c) it remains the same d) it drops to zero 11. which element is least likely to gain an electron? a) f b) o c) he d) cl

Explanation:

• For question 9: As you move across a period, the number of protons in the nucleus increases. This leads to a greater nuclear - charge, which pulls the electrons closer, decreasing the atomic radius. Electron - shielding remains relatively constant across a period, and no new energy levels are added. Atoms do not gain enough electrons to cause significant repulsion across a period.
• For question 10: As you move down a group, the outermost electrons are in higher energy levels, farther from the nucleus. The increased distance and shielding effect make it easier to remove an electron, so ionization energy decreases.
• For question 11: Helium (He) has a full outer - shell (2 electrons in its 1s orbital), making it extremely stable. It has no tendency to gain an electron. Fluorine (F), oxygen (O), and chlorine (Cl) are non - metals that readily gain electrons to achieve a stable electron configuration.

Answer:

1. B. Number of protons increases, pulling electrons in
2. B. It decreases
3. C. He