Question

The atom’s first electron shell, which is innermost and closest to the
nucleus, can hold ________________ electrons.
d. The second shell can hold more; __________ electrons.
e. The third shell can hold 8 electrons in its lower subshell and up to a total of
_____________electrons.
Collaborative Catch-up: Atomic Structure
1. Identify the atomic weight and atomic number of oxygen. If this was a neutral atom,

Answer 1

a. The atom’s first electron shell, which is innermost and closest to the nucleus, can hold **2** electrons.

b. The second shell can hold more; **8** electrons.

c. The third shell can hold 8 electrons in its lower subshell and up to a total of **18** electrons (when considering higher subshells as well).

Regarding the collaborative catch-up on atomic structure:

1. The atomic weight of oxygen is approximately **16 amu (atomic mass units)** (more precisely about 15.999), and its atomic number is **8**.

For a neutral atom of oxygen, it would have **8 protons** and **8 electrons**. The number of protons is equal to the atomic number (the defining characteristic of an element), and in a neutral atom, the number of electrons equals the number of protons.