1	Atoms, Molecules, and Ions Chapter 2
2	Law of conservation of mass Mass is neither created nor destroyed in a chemical reaction. In an ordinary chemical reaction, the total mass of reacting substances is equal to the total mass of products formed.
3	Law of Constant composition (Law of Definite Proportions) Different samples of a pure chemical substance always contain the same proportion of elements by mass. The relative amount of each element in a particular compound is always the same, regardless of the source of the compound or how it was made.
4	Atomic Theory Elements (matter) is composed of small, indivisible particles called atoms. Atoms of a given element are identical in mass and behavior. Atoms of different elements differ in mass and behavior. Chemical combination of elements to make different substances occurs when atoms join together in small whole number ratios. Chemical reactions only rearrange the way the atoms are combined; the atoms themselves are not changed.
5	Law of Multiple Proportions If two elements combine in different ways to form different substances, the mass ratios are small, whole number multiples of each other.
6	Sub Atomic Particles
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8	"Thompson – determined charge/mass ratio..." Thompson – determined charge/mass ratio for an electron. Charge/mass = 1.758820 x 10⁸ C/g Millikan – determined the charge on an electron. Charge = 1.602176 x 10^-19 C Leading to the mass of an electron mass = 9.109382 x 10^-29 g
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11	Atoms are composed of
12	Atomic Number = Z = number of protons in an atom. = number of electrons in a neutral atom.
13	Isotopes Atoms which differ only in the number of neutrons present in the nucleus.
14	Atomic Mass The weighted average of the isotopic masses of an element’s naturally occurring isotopes. Atomic mass unit - amu
15	Isotopes of Neon
16	Isotopes of Neon
17	Classification of Matter
18	Covalent Compounds Discrete molecules where atoms are joined by shared electron bonds or covalent bonds Composed of nonmetals bonded to nonmetals Represented by structural formulas
19	Ionic compounds Composed of ions held together by electrostatic attractions Composed of metals bonded to nonmetals Represented by empirical formulas
20	Metallic compounds Composed of metals bonded to metals Will see more in chem 142