Chapter 2 from Chem 1303 Flashcard

John Dalton’s Atomic Theory
1. Elements: are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements

2. Compounds: are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. (incorporates laws of definite proportions and multiple proportions)
a. Law of definite proportions: different samples of the same compound always contain its constituent elements in the same proportions by mass.
b. Law of multiple proportions: If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers (use CO and CO2 as an example: 12 to 16 versus 12 to 32.)
c. Law of conservation of mass: matter can be neither created nor destroyed

3. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.

Atom
the basic unit of an element that can enter into chemical combinations
Atoms composed of ____, _______, and _______.
electrons

protons

neutrons

charge and mass of electrons
negatively charged

mass= 9.1096 x 10^-31 kg

charge and mass of protons
positively charged

mass= 1.6727 x 10^-27 kg

charge and mass of neutrons
neutral

mass= 1.6750 x 10^-27 kg

3 kinds of particles and/or radiation emitted by radioactive substances
alpha particles (helium nuclei)

beta (?) particles (electrons)

gamma rays

Atomic number
Z

number of protons in nucleus= number of electrons in a neutral atom

mass number
A

sum of protons plus number of neutrons in nucleus

Element
a form of matter in which all of the atoms have the same atomic number
isotopes
when two atoms have the same number of protons but a different number of neutrons

Therefore, two atoms of the same element can have different mass numbers

Special names 1A
alkali metal
Special names 2A
alkaline earth metals
special names 7A
halogens
special names 8A
noble gases
Molecule
an aggregated of at least two atoms in a definite arrangement held together by chemical forces (bonds)
7 diatomic elements
H, N, O, F, Cl, Br, I

H2, N2, O2, F2, Cl2,Br2, I2 diatomic

Ion
charged species formed from a neutral atom or molecule when electrons are gained or lost as a result of a chemical change
cations
positive
anions
negative
Chemical Formulas
express the composition of molecules and ionic compounds in terms of chemical symbols
Molecular formula
shows the exact number of atoms of each element in the smallest unit of a substance

EX: Methane = CH4

Allotrope
one of two or more forms of an element

Ex: oxygen, O2 and ozone, O3

Empirical formula
tells which atoms are present and the simplest whole number ratio of the atoms (determined by experiment)

glucose contains C, H, O in 1:2:1 ratio
therefore the empirical formula is CH2O

ionic compounds
discrete molecules are not present; ionic compounds are represented by their empirical formulas
Four types of compounds
1. ionic
2. molecular (covalent)
3. acids
4. bases, hydrates
mono-
1
di-
2
tri-
3
tetra-
4
penta-
5
hexa-
6
hepta-
7
octa-
8
nona-
9
deca-
10
acid
a substance that yields hydrogen ions (H+) when dissolved in water
oxoacids
acids that contain hydrogen, oxygen, and another element
base
a substance that gives hydroxide anions (OH-) when dissolved in water
hydrates
compounds that have a specific number of water molecules attached

EX: BaCl2•2 H2O barium chloride dihydrate

Sr(NO3)2•4 H2O strontium nitrate tetrahydrate

hydrocarbons composed of what?

Alkanes

composed of carbon and hydrogen

CnH(2n+2)

CH4= methane
C2H6=ethane
C3H8=propane
C4H10=butane
C5H12=pentane
C6H14=hexane
C7H16=heptane
C8H18=octane
C9H20=nontane
C10H22=decane

NH4+
ammonium
H3O+
hydronium
Hg2 2+
mercury I
CN-
cyanide
OCN-
cyanate
SCN-
thiocyanate
OH-
hydroxide
C2H3O2-
acetate
MnO4-
permanganate
NO3-
nitrate
NO2-
nitrite
H2PO4-
dihydrogen phosphate
HCO3-
hydrogen carbonate or bicarbonate
HSO4-
hydrogen sulfate
HSO3-
hydrogen sulfite
ClO4-
perchlorate
ClO3-
chlorate
ClO2-
chlorite
ClO-
hypochlorite
O2 2-
peroxide
C2O4 2-
oxalate
CrO4 2-
chromate
Cr2O7 2-
dichromate
HPO4 2-
hydrogen phosphate
CO3 2-
carbonate
SO4 2-
Sulfate
SO3 2-
sulfite
S2O3 2-
thiosulfate
PO4 3-
phosphate
AsO4 3-
aresenate

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