What element has 3 protons and 4 electrons?

Li⁻

Explanation:

# of protons = # element on the Periodic Table.

# of protons (+) + # of electrons (-) = overall charge

3 protons is the 3rd element on the Periodic Table: Lithium

All elements on the Periodic Table have a neutral charge. Lithium neutral has 3 protons and 3 electrons.

We are given 4 electrons; 3 + -4 = -1 charge overall.

Therefore, our ion is Li⁻

answerdmitry mendeleyev made a workable classification of the elements