Question

This is the listing for the element lithium (Li) from the periodic table of the elements.



A student in physical science is making a poster of a model of a lithium atom using this key:



Based on this information, which model best represents a neutral atom of lithium for the poster?

a




b




c




d

Answer 1

A neutral lithium atom has atomic number 3 (so 3 protons) and about mass 7 (atomic mass ≈ 6.94 → 7 total nucleons), so it has 4 neutrons. A neutral atom has the same number of electrons as protons, so Li has 3 electrons. Those electrons fill shells as 2 in the first shell and 1 in the second.

So pick the model that shows:
- Nucleus with 3 protons and 4 neutrons, and
- Electrons arranged 2 in the inner shell and 1 in the outer shell.

If you can tell me which option (a–d) matches that description or post the pictures, I’ll confirm which letter is correct.