Question

the smallest unit of an element that retains its chemical properties, consisting of protons, neutrons, and electrons.
a chemical rule that states atoms are most stable when they have eight electrons in their outermost electron shell, like noble gases.
atoms of the same element that have different numbers of neutrons but the same number of protons.
the weighted average mass of an atom, protons plus neutrons.
the total number of protons in the nucleus of an atom, which defines the element.
a positively charged ion formed when an atom loses one or more electrons.
an atom or molecule with a net electrical charge due to the loss or gain of one or more electrons.
a negatively charged ion formed when an atom gains one or more electrons.

Explanation:

1. The smallest unit of an element retaining chemical properties with protons, neutrons, and electrons is an atom.
2. The chemical rule stating atoms are most stable with eight electrons in the outermost shell is the octet - rule.
3. Atoms of the same element with different neutron numbers but same proton numbers are isotopes.
4. The weighted - average mass of an atom (protons plus neutrons) is the atomic mass.
5. The total number of protons in an atom's nucleus defining the element is the atomic number.
6. A positively - charged ion formed when an atom loses electrons is a cation.
7. An atom or molecule with a net electrical charge due to electron loss or gain is an ion.
8. A negatively - charged ion formed when an atom gains electrons is an anion.

Answer:

1. Atom
2. Octet rule
3. Isotopes
4. Atomic mass
5. Atomic number
6. Cation
7. Ion
8. Anion