Atoms & Matter

Atoms & Matter

Author: John Lui

Understand the basics behind matter.  Learn about the basics of atomic structure and the law of conservation of mass. 

Students will learn how matter is made of atoms and that matter cannot be created or destroyed.

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Atoms to Molecules

What is Matter?

To understand minerals, we must first understand matter. Matter is the substance that physical objects are made of. There are three common states of matter, solid, liquid, and gas.  Another state of matter is plasma where atoms are so excited, they lose control of their electrons.

Atoms and Elements

The basic unit of matter is an atom ( Figure below ). At the center of an atom is its nucleus. Protons are positively charged particles in the nucleus. Also in the nucleus are neutrons with no electrical charge. Orbiting the nucleus are tiny electrons. Electrons are negatively charged. An atom with the same number of protons and electrons is electrically neutral. If the atom has more or less electrons to protons it is called an ion. An ion will have positive charge if it has more protons than electrons. It will have negative charge if it has more electrons than protons.

The nucleus of an atom is made up of protons (blue) and neutrons (red). Electrons (black) orbit around the nucleus.

An atom is the smallest unit of a chemical element . That is, an atom has all the properties of that element. All atoms of the same element have the same number of protons.

Molecules and Compounds

A molecule is the smallest unit of a chemical compound . A compound is a substance made of two or more elements. The elements in a chemical compound are always present in a certain ratio.

Water is probably one of the simplest compounds that you know. A water molecule is made of two hydrogen atoms and one oxygen atom ( Figure below ). All water molecules have the same ratio: two hydrogen ions to one oxygen ion.

Source: ck12

Conservation of Mass

During a chemical reaction, matter is not created or destroyed. The basic understanding that all of the chemicals interacting in a chemical reaction are still present at the end is called the conservation of mass.

The principle of conservation of mass states that the total mass of the reactants at the beginning of a chemical interaction are equal to the total mass of the products.


It doesn't always seem like the matter in a chemical reaction is being conserved. When wood is burned in a fire, much of the matter in the fire is able to escape into the environment. If a dome was placed over a wood fire and it contained all of the gases and products of the fire, the mass of the wood before the fire and the products of the fire would have the same mass.

What is Atom?

Source: MonkeySee