Notes

2.1
Dalton's atomic theory
- matter is composed of exceedingly small particles called atoms; an atom is the smallest unit of an element that can participate in chemicals change
- an element consists of only one type of atom that has a mass that is characteristic of the element and is the same for all atoms of that element; a macroscopic sample of an element contains an incredibly large amount of atoms that all have identical properties
- atoms of one element differ in properties from atoms of all other elements
- a compound consists of atoms of two or more elements combined in a small, whole-number ratio; in a given compound, the number of atoms of each of its elements are always present in the same ratio
- atoms are neither created nor destroyed during a chemical change, but are instead rearranged to yield substances that are different from those present before the change

law of multiple proportion states that when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small, whole numbers

2.2
- JJ Thompson used cathode ray tube to propose that the electron particles were attracted by positive charges and repelled by negative charges, meaning that they themselves were negative

- Robert A. Molikan used oil drop experiment that were electrically charged by friction to determine that the charge of a single electron was 1.6*10^-19

- Thomson proposed the plum pudding model of electrons in 1904, which described a positively charged mass with an equal amount of negative charge in the form of electrons embedded in it, since all the atoms are elctrically neutral

- Ernest Rutherford performed a series of experiments using a high-speed beam and positively charged alpha particles, shooting them through a thin gold foil, discovering that the volume of an atom mainly consists of empty space with the center being a small, relatively heavy, charged body (the nucleus)
- Rutherford then proposed a model in which an atom consists of a small positive nucleus, and named the center hydrogen nucleus a "proton"

- In the early 1900s, scientists discovered substances that appeared to be new elements that were chemically identical but had a different atomic mass, they were called "isotops"

-In 1932, James Chadwick found evidence of neutrons, uncharged, subatomic particles with a mass that was the same as protons; this discovery explained the existence of isotopes

2.3
atomic mass unit - amu
fundamental unit of charge - e
dalton - Da
unified atomic mass unit - u
atomic number (Z)
mass numver (A)
ion - when the numbers of these subatomic particles are not equal, atom is electrically charged
chemical symbol - abbreviation that is used to indicate an element or an atom of an element

- atomic mass of a single atom is approximately equal to its mass number

average mass = summation (fractional abundance x isotopic mass)

for example, 19/9% of boron atoms are 10B with mass of 10.0129 amu and remaining 80/1% are 11 B with mass of 11.0093 amu
(0.199*10.0129)+(0.801*11.0093) = 1.99 amu + 8.82 amu = 10.81 amu

2.4
molecular formula - representation of a molecule hat uses chemical symbols to indicate the types of atoms followed by subscripts to show the numver of atoms of each type in the molecule

structural formula - compound that gives the same information as its molecular formula but also shows how the atoms are connected in the molecule

empirical formula - composition of compounds that indicates the types of atoms present and the simple whole-number ratio of the number of atoms or ions within the compound

isomers - compounds with the same chemical formula but different molecular structures
structural isomers - compounds where molecules differ in how atoms are connected to each other
spatial isomers - where relative orientations of atoms in space can be different

- a mole of substances is that amount in which there are 6.022*10^23

Avogadro's number (Na) - large numver that is fundamental constant 6.022*10^23

molar mass - mass in grams of 1 mole of that substance (g/mol)