Chemistry 1st Semester Exam

accuracy

closeness to “true” value

precision

repeatability of a measurement

absolute error

|actual value - ovserved value|

percent error

(absolute error/actual error) x 100

adding & subtracting sig figs

keep the lease amount of decimal places

multiplying & dividing sig figs

keep the least amount of sig figs

kilo-

1000 or 10³

hecto-

100 or 10²

deca-

10 or 10^1

deci-

0.1 or 10^-1

centi-

0.01 or 10^-2

milli-

0.001 or 10^-3

kelvin

C + 273

mixture

consists of two or more different particles

element

group/collection of 1 type of atom

compound

2 or more different elements

physical properties

state of matter, observations made with senses

extensive properties

based on the amount of matter (ex. mass, volume, length)

intensive properties

based on type of matter (ex. density, boiling point, colour)

chemical properties

substance’s ability to undergo a chemical change

signs of chemical reaction

change in temperature, change in colour, production of light, production of gas, formation precipitate

filtration

separates a solid from a liquid

distillation

separates a dissolved substance from a liquid

density

mass over volume

atomic number

number of protons in an atom (also electrons)

general isotope formula

(Mass Isotope A X Abundance as a decimal) + (Mass Isotope B X Abundance as a decimal)

atomic orbital

region of space where there is a high probability of finding e-

aufbau principle

electrons fill the lowest energy orbitals first

pauli exclusion principle

no more than 2 electrons can occupy the same orbital, electrons in the same orbital must have opposite spin

hund’s rule (bus seat rule)

all orbitals in a sublevel must be singly occupied before pairing, electrons in singly occupied orbitals have the same spin

electron configuration

1s² 2s²

ground state

e- occupy the lowest energy levels possible

excited state

e- gain energy and jump to higher energy levels

periodic table

group: vertical column, period: horizontal row

metals

good conductors, solids at room temperature, malleable

nonmetals

greater variation in physical properties, poor conductors

metalloids

elements on the staircase, semiconductors

atomic radius

half the distance between the nuclei of two joined identical atoms

atomic radius trend

increases down group, decreases left to right across a period

ions

ana atom that has lost or gained an electron, cations (+) & anions (-)

ionization energy

the energy required to remove an electron from an atom

ionization energy trend

increases going up a group, increases left to right across a period

electronegativity

the ability of an element to attract e- from a different atom

electronegativity trend

increases going up a group, increases across a period

valence electrons

e- in the outermost energy level of an atom

cations

metals, groups: 1, 2, 13, loses VE to achieve an octet

anion

nonmetals, groups: 15, 16, 17, gains VE to achieve an octet

ionic compounds

composed of oppositely charged ions (anions & cations)

binary ionic compound

2 elements

ternary ionic compound

3+ elements, polyatomic ion

transition metals

name of element plus a roman numeral

covalent bond

bond formed by the sharing of e- between atoms (2 nonmetals)

ionic bond

electrostatic attraction that binds oppositely charged ions (metal + nonmetal)

monatomic elements

most elements exist as single/individual atoms

diatomic elements

a molecule composed of 2 identical covalently bonded atoms

lone pair

unshared pair of electrons

single covalent bonds

atoms bonded together by sharing one pair of electrons

double covalent bonds

atoms share two pairs of electrons

triple covalent bonds

atoms share 3 pairs of electrons

bond dissociation energy

the energy required to break a bond between two covalently bonded atoms

VSPER theory

valence shell electron pair repulsion theory

electron domains

2 electron domains = linear, 3 electron domains = trigonal planar, 4 electron domains = tetrahedral

nonpolar covalent bond

bonding e- shared equally between 2 atoms

polar covalent bond

bonding e- shared unequally between 2 atoms

mole

6.022 × 10²³ items

representative particles

atom, molecule, formula unit

molar mass

mass of one mole of an element (atomic mass but expressed as grams per mole)

diatomic elements

Br₂, I_2, Cl_2, H_2, 0_2, F₂

STP

standard temperature and pressure

molar volume

at STP, 1 mole of any gas occupies a volume of 22.4L

percent composition

the percent by mass of each element in a compound (mass of element/mass of compound x 100)

empirical formula

the lowest whole number ratios of the elements

molecular formula

the actual ratio of elements