Which of he following would be most affected by a change in the atmosphere

D . The atomic number and atomic mass decrease from left to right across a period;

energy levels increase from top to bottom down a group.

Explanation:

On the periodic table, elements are arranged based on the periodic law. This law states that "the properties of elements are a periodic function of their atomic number".

The atomic number is the number of protons in an atom.

Atomic mass is the number of protons and neutrons in an atom

The energy level is the number of shells in an atom

As we move from left to right on the periodic table, both atomic mass and atomic number increases. Also, down a group, the energy level increases as the number period increases. From left to right, the energy level stays the same.