There are many examples of atom, 106 in fact. Look at the Periodic Table of the elements.
Gold
Molecules are not atoms, so I assume they can be classified as non-examples of atoms. Water is a molecule, and therefore not an atom. Water is comprised of two hydrogen atoms and one oxygen atom. Carbon is an atom.
Be the Club not the Atom
An atom is the smallest unit of an element that still maintains the physical properties of the element. Examples are: hydrogen, oxygen, gold, aluminum, neon, silver, carbon, potassium.
An atom is the basic unit of matter consisting of a nucleus (protons and neutrons) surrounded by electrons. Two examples of atoms are hydrogen, which has one proton and one electron, and oxygen, which has eight protons, eight neutrons, and eight electrons.
Mass number is the total number of protons and neutrons in an atom's nucleus. Non-examples of mass number would include atomic number (number of protons in an atom), electron configuration (arrangement of electrons in an atom), and atomic mass (average mass of an atom, taking into account all isotopes).
An example could be a diagram, or picture, or equation, etc.
Examples: a neutral atom, a neutron, a neutrino, etc.
An atom whose nucleus decays over time is called radioactive. Some examples of radioactive substances are uranium, plutonium, and einsteinium.
Examples of gases: oxygen, helium, radon, nitrogen, etc.
A monatomic molecule contains only one atom. It is a single atom that is chemically stable. Examples include noble gases like helium and neon.
Compound is made out of different types of atoms. Some of the examples are, H20, Co2, KMno4. Elements are made out of only the same atom.