The number of protons plus the number of neutrons is the mass number. When an acid is added to a base, a chemical reaction occurs. The reaction produces water and a salt. Also, each elemnet is represented by a symbol- a capital letter followed by one or two lowercase letters. Atoms are the building blocks of matter.
All atoms have a core called a nucleus containing protons and neutrons.
Protons have a positive electric charge. Neutrons have no electric charge. The number of protrons equals the number of electrons. A property is a quality or characteristic of matter. A compound is a substance made of two or more elements whose atoms are chemically combined.