1. The Nature of Matter 2.1

2. Atom A basic unit of matter.

3. Nucleus The center of the atom which contains the protons and neutrons; in cells, structure that contains the cell’s genetic material (DNA) and controls the cell’s activities.

4. Electron Negatively charged particle; located outside the atomic nucleus.

5. Molecule Smallest unit of most compounds.

6. Van Der Waals Forces A slight attraction that develops between the oppositely charged regions of nearby molecules.

7. Element A substance that cannot be broken down into simpler substances by ordinary chemical or physical means.

8. Ion An atom or a molecule that possesses an electrical charge.

9. Covalent Bond A bond that forms when atoms share electrons.

10. Ionic Bond A bond that forms between negative and positive ions.

11. Compound A substance formed by the chemical combination of two or more elements in definite proportions and usually having properties different from those of its constituent elements.

12. Isotope An atom with the same number of protons but different numbers of neutrons for a given element; an isotope’s mass number is different from that of the given element.

13. Key Concept What three subatomic particles make up atoms? The subatomic particles that make up atoms are protons, neutrons, and electrons.

14. Key Concept How are all of the isotopes of an element similar? Because they have the same number of electrons, all isotopes of an element have the same chemical properties.

15. Key Concept What are the two main types of chemical bonds? The main types of chemical bonds are ionic bonds and covalent bonds.