chem final review

atom

the smallest unit of matter that keeps the properties of that element

element

a pure substance made of only one type of atom

compound

a PURE substance that has 2+ elements chemically bonded together. (certain fixed ratios)

mixture

a combination of substances that are not bonded chemically

homogeneous mixture

a mixture that physically is uniform, so no distinct seperation. (ex: salt water)

heterogeneous mixture

a mixture that has different visible substances

pure substance

matter that has consistent properties

physical PROPERTY

a characteristic that can be observed and doesn’t change the chemicals identity. ex: density, colour, melting point

chemical PROPERTY

a characteristic that describes a substances’ ability to undergo chemical change. ex: flammability, reactivity

physical CHANGE

a change in state or form without chemical identity changing

chemical CHANGE

a process that FORMS one or more new substances

evidence of chemical change (signs that chemical reaction has occured)

• gas production

• colour change

• temperature change

• light emitted

• precipitate formation

proton

positively charged particle located in the nucleus

• The amount of protons is direct to an atom’s atomic number

neutron

neutral particle located in the nucleus

• mass number - atomic number

electron

negatively charged particle found outside the nucelus

• directly connected to atomic number

isotope

atoms from the same element but has different numbers of neutrons.

• some have extra neutrons, making heavier or lighter. ex: regular carbon has 6 neutrons, another carbon isotope has 8 neutrons.

Ion

an ion that has either gained or lost electric charge, by gaining or losing electrons

cation

positively charged ion formed by losing electrons

anion

negatively charged ion formed by gaining electrons

ionic compound

compound formed between metals and nonmetals

molecular compound

compound formed between nonmetals

polyatomic ion

group of atoms that are covalently bonded. *atoms sharing electrons*

mono, di, tri, tetra, penta

1, 2, 3, 4, 5

single replacement reaction

A + BC → AC +B

1 mole

= 6.022 × 10²³ particles → avogadros number

a mole is like a “dozen” → a mole means 6.022 × 10²³ items.

stoichiometry

using balanced equations to calculate quanitites in reactions

limiting reactant

reactant that is used up first so it limits the product formed

excess reactant

the reactant that remains even after reaction is complete

theoretical yield

the maximum amount of product predicted by stoichiometry

actual yield

the amount of product actually obtained experimentally

percent yield

the efficiency of a reaction

forumla: % yield = (actual yield/ theoretical yield) x 100

percent composition

percent by mass each element is a part of and contributes to a compound

% in element = (mass of element in compound/ molar mass of compound) x 100

empirical vs molecular formula

MF: actual number of atoms in molecule while the empirical is condensed version of that

valence electrons

electrons in the outermost energy level

aufbau priciple

electrons fill lowest-energy orbitals first.

hund’s rule

electrons fill orbitals singly before pairing

pauli exclusion principle

an orbital can hold at most two electrons with opposite spins

atomic radius

• size of an atom

• increases down a group, decreases across period

ionization energy

• energy required to remove an electron

• decreases down a group, increases across period

electronegativity

• ability of an atom to attract electrons in a bond

• decreases down a group, increases across period

covalent bond

bond formed by sharing electrons

ionic bond

bond formed from electron transfer

VSEPR theory

electron pairs repel and arrange to minimize repulsion

molecular geometry: linear, trigonal planar, tetrahedral, bent, trigonal pyramidal

180, 120, 109.5, less than 109.5, less than 109.5

polar molecule

molecule with uneven charge distribution

nonpolar molecule

molecule with even charge distribution

IMF

attractions between molecules

london dispersion forces

weak, temporary attractions that are shown in all molecules

dipole-dipole forces

attractions between polar molecules

hydrogen bonding

strongest IMF that has H bonded to N,O, or F

imf strength effects

• higher boiling point

• higher melting point

• higher viscosity

• lower vapor pressure

precision

how close repeated measurements are to each other

accuracy

how close a measurement is to the true value

experimental error

factors causing inaccurate results