Atoms, Ions, and Molecules: The Building Blocks of Living Things

Vocabulary flashcards covering key terms from pages 3–5 about atoms, ions, molecules, and related concepts.

Element

Chemical substance made of only one type of atom.

Atom

Smallest unit of an element; electrically neutral.

Nucleus

Center of the atom composed of protons and neutrons.

Proton

Positive charge (+1) particle in the nucleus.

Neutron

Neutral charge particle in the nucleus.

Electron

Negatively charged particle orbiting the nucleus (−1).

Atomic number

Number of protons in an atom's nucleus.

Mass number

Sum of protons and neutrons in an atom.

Hydrogen

One of the four elements that make up about 96% of matter in organisms.

Carbon

One of the four elements that make up about 96% of matter in organisms.

Nitrogen

One of the four elements that make up about 96% of matter in organisms.

Oxygen

One of the four elements that make up about 96% of matter in organisms.

Water

A simple molecule mentioned as a building block of chemical evolution.

Carbon dioxide

A simple molecule mentioned as a building block of chemical evolution.

Molecule

Two or more atoms bonded together.