| A | B |
|---|
| Matter | Anything that occupies space and has mass. |
| Mass | The quantity of matter that an object has. |
| Elements | Pure substances that cannot be broken down chemically into simpler kinds of matter. |
| Atom | The simplest particle of an element that retains all of the properties of that element. |
| Nucleus | The central core of an atom that consists of two kinds of particles. |
| Proton | The particles with positive charges. |
| Neutron | The particles without charges. |
| Atomic number | The number of protons in an atom. |
| Electrons | Negatively charged particles. |
| Energy levels | The different levels where electrons are held. They surround the nucleus. |
| Compound | A pure substance that is made up of atoms of two or more elements. |
| Chemical reactions | Elements combining in ways that cause their atoms to become stable. |
| Bonds | When atoms are rearranged and new attachments are formed. |
| Covalent bond | When two atoms share one or more pairs of electrons. |
| Molecule | The simplest part of a substance that retains all of the properties of the substance and that can exist in a free state. |
| Ion | An atom or molecule with an electrical charge. |
| Ionic bond | When positive and negative electrical charges are attracted to each other. |
| Energy | The ability to do work or cause change. |
| Free energy | The energy in a system that is available for work. |
| State | The rate at which atoms or molecules of a substance move to determine, gas, solid, liquid. |
| Reactants | What is reacting and is shown on the left side of a chemical equation. |
| Products | What is produced and is shown on the right side of a chemical equation. |
| Exergonic reactions | Chemical reactions that involve a net release of free energy. |
