The characteristic way in which atoms of an element react is most related to the
a. number of electrons in the outermost shell.
b. number of electrons in the innermost shell.
c. number of neutrons in the nucleus.
d. size of the nucleus.

A. Number of electrons in the outermost shell

Explanation:

The outermost electrons are the farthest from the nucleus.

They are the least tightly held, so they are most likely to be involved in chemical reactions.

B. is wrong. The innermost electrons are too tightly held to react.

C. and D. are wrong. The particles in the nucleus do not take part in chemical reactions.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.