4. Protons are

a. located in the shells.
b. part of the atomic nucleus.
c. negatively charged.
d. uncharged particles

5. Particles of an atom located in the outermost shell and available for chemical bonding are called
a. valence electrons.
b. isotopes.
c. excess electrons.
d. neutrons.

6. Isotopes are atoms with
a. the same number of electrons and protons.
b. different numbers of protons and electrons.
c. the same numbers of protons but a different number of neutrons.
d. different numbers of electrons.