Notes

Terms 6.1
1. Chemistry is the organized study of the composition and interactions of matter
2. John Dalton proposed the atomic theory of matter (the foundation for the understanding of matter), which states
that all matter is composed of tiny particles called matter (atoms), and that they can combine in various ways to form substances
3. Elements are composed of a single type of atom.
4. Compounds are composed of more than one type of atom linked together.
5. Molecules are groups of atoms linked together.
6. Mixtures are physical combinations of elements and compounds.
7. Alloys are metal mixtures.
8. Chemical symbols are unique abbreviations usually based on either its common or Latin name.
Terms 6.2
9. Subatomic particles are tiny particles within an atom.
10. The nucleus is the atom's dense central core.
11. Nucleons are the subatomic particles within the nucleus. There are two types: protons and neutrons.
12. Protons have a positive electrical charge. They are the most important part of the atom because they determine its identity.
13. The atomic number is the number of protons in the nucleus of the atom.
14. A neutron has no electrical charge.
15. Isotopes are atoms that are the same element but have different numbers of neutrons.
16. Quarks are the subatomic particles that make up protons and neutrons. There are two types: up quark(+1/3) and down quark
(-1/3). Three quarks are needed to make a proton or a neutron.
17. Electrons are found outside the nucleus. They are very light and have a negative electrical charge.
18. Electron shells (2n2) are the layers surrounding the nucleus. Each can hold a certain number of electrons. Also called energy levels.
19. Ions are atoms that have electrical charge because of losing or gaining electrons.
20. Anions are negatively charged ions.
21. Cations are positively charged ions.
22. An atom's mass number is the total number of protons and neutrons in the nucleus.
23. Atomic mass units are the units used to measure small particles. The mass of an atom in atomic mass units is approximately equal
to the mass number.
24. The average atomic mass is the average mass of all the natural isotopes of an element.
25. The quantum theory states that tiny particles such as electrons do not absorb or release energy in a smooth flow.
26. Electrons change shells when they gain or lose energy. When this happens, it is called a quantum jump.
27. The Bohr model is the most familiar model of the atom. It pictures the nucleus surrounded by electrons that move in circular orbits.