Protons and neutrons are located inside the atom or nucleus of an atom and electrons around it.
The nucleus of an atom carries positive charge because it bears charge from the protons which are present in the nucleus (and we know neutron doesn’t have any charge).
Some of the Key Words:
a. Valence shell: The outermost shell.
b. Valence electrons: The electrons present in the outermost shell or valence shell.