Atoms, Molecules, and Chemical Bonds

Matter

Anything that occupies space and has mass.

Chemical Elements

Substances that cannot be broken down into other substances; a total of 25 are essential for life.

Atom

The smallest unit of matter that retains the properties of an element.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Neutron

An electrically neutral subatomic particle found in the nucleus of an atom.

Electron

A negatively charged subatomic particle that orbits the nucleus of an atom with no discernable mass.

Atomic Number

The number of protons in an atom, which determines the element.

Mass Number

The sum of the number of protons and neutrons in an atom.

Electron Shells

Specific distances at which electrons orbit the nucleus of an atom.

Covalent Bond

A bond formed when two atoms share outer-shell electrons.

Polarity of Water

Causes water to form hydrogen bonds due to uneven sharing of electrons.

Hydrogen Bond

An electrical attraction between neighboring water molecules.

Solvent

A substance, like water, that facilitates chemical reactions by dissolving many chemical substances.

Hydrophilic Molecules

Molecules that attract water.

Hydrophobic Molecules

Molecules that do not attract water.

Dehydration Synthesis

A reaction where water is removed to join monomers into polymers.

Hydrolysis

A reaction that adds water to break down polymers into monomers.