Matter is all around you. Atoms and compounds are made up of very small parts of matter. Matter is defined as anything with mass that takes up space.

A atom is the smallest unit of matters that forms a chemical element. Every solid, liquid, gas and plasma is composed of atoms. Atoms are very small, typically around 100 picometers.

An element is a substance consisting only of atoms that all have the same number of protons in their atomic nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances.

The periodic table is a tabular array of the chemical elements organized by atomic numbers, from the element with the lowest atomic number, hydrogen, to the element with the highest atomic number, oganesson.

A molecule is a group of two or more atoms that form the smallest identifiable unit into a pure substance that can be divided and still retain the composition and chemical properties of that substance.

A compound is a substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds.

A coefficient is a number placed in front of a chemical symbol or formula. It shows how many atoms or molecules of the substance are involved in a reaction.

A subscript is a character, usually a letter or number that’s printed slightly below and to the side of another character. Subscripts are commonly used in chemical formulas.