What is the structure of the atoms of hydrogen, helium and lithium?

Hydrogen
Refers to non-metals. The nuclear charge is 1. The atomic weight is 1.00 amu.
The hydrogen atom has a positively charged nucleus (+1), 1 proton and one electron.

Helium
The ordinal number is 2. The charge of the nucleus is +2. Atomic weight – 4.003 amu
A helium atom consists of a positively charged nucleus (+2) (two protons, two neutrons), around which two electrons move along the atomic shell.

Lithium
The ordinal number is 3. The charge of the nucleus is +3. Atomic weight – 6.941 amu.
The lithium atom has a positively charged nucleus (+3), which has 3 protons and 4 neutrons. 3 electrons move in two orbits around the nucleus.