Chemistry First Year

elements

primary constituents, cannot be broken down into simpler substances

compounds

atoms of different elements chemically bonded in a fixed ratio

homogenous

uniform composition and properties

heterogenous

nonuniform composition and properties

sublimation

solid to gas

deposition

gas to solid

isotopes

atoms of the same element with different properties

Avogadro’s Law

equal volumes of any gases at same temperature and pressure contain equal numbers of molecules

assumptions of ideal gases

1. molecules are in constant random motion

2. collisions between molecules are elastic

3. volume occupied is negligible compared to volume of container

4. no imfas

5. kinetic energy is proportional to Kelvin

when do gases divert from idea gases

high pressure and low temperature

boyle’s law

pressure is inversely proportional to volume

charles’ law

volume is proportional to temperature at constant pressure

gay-lussac’s law

pressure is proportional to temperature at constant volume

Molar Volume of gas

volume occupied by 1 mol of ideal gas at STP

1000 Pa in kPa

1 kPa

1cm³ in dm³

1 × 10^-3 dm³

electromagnetic spectrum

range of wavelengths/frequencies of electromagnetic radiation

radiowaves

low energy, low frequency, high wavelengths

gamma rays

high energy, high frequency, low wavelength

transition to n=1

UV

transition to n=2

visible

transition to n=3

infrared

ionic bond

electrostatic attraction between oppositely charged ions

ammonium

NH₄⁺

hydroxide

OH^-

nitrate

NO₃^-

hydrogencarbonate

HCO₃^-

carbonate

CO₃^2-

sulfate

SO₄^2-

phosphate

PO₄^3-

covalent bonding

electrostatic attraction between shared pair of electrons and positively charged nuclei

VESPR

valence shell electron pair repulsion predicts shapes of molecules

linear geometry

2 domains, 180

trigonal planar geometry

3 domains, 120

tetrahedral geometry

4 domains, 109.5

london dispersion forces

all molecules experience due to temporary instantaneous dipoles

dipole-induced dipole

between a polar and non-polar molecule where a permanent dipole incudes a temporary dipole in the non-polar molecule

dipole-dipole

involve permanent dipoles between neighboring polar molecules

hydrogen bonds

molecules that contain bonds with hydrogen and F, O, N

properties of simple molecular covalent substances

volatile, not conductors, solubility depends on solvent

properties of giant covalent substances

non volatile, not conductors, generally insoluble

properties of ionic bonds

non volatile, hard and brittle, can conduct electricity when molten or aqueous

metallic bond

electrostatic attraction between a lattice of cations and a sea of delocalized electrons

properties of metallic bonds

good electrical and thermal conductors, malleable, volatility decreases as radius decreases

alloys

metals mixed with other elements that maintain most metallic characteristics

polymers

covalently bonded materials with low conductivity and volatility

alkali metals

group 1, reactive, reacts with water to from metal hydroxides, reacts with halogens to form ionic/metallic halides

halogens

group 17, diatomic elements, reactivity decreases down a group

noble gases

group 18, least reactive, colorless gases

atomic radius trend

increases down a group, decreases across a period

atomic radius

half distance between neighboring nuclei

ionization energy

energy required to eject 1 mole of electrons from 1 mole of gaseous atoms

ionization energy trend

decreases down a group, increases across a period

electron affinity

energy change when 1 mole of electrons is added to 1 mole of gaseous atoms

electron affinity trend

increases across a period

electronegativity

measure of an atom’s ability to attract a pair of electrons from a chemical bond to itself

electronegativity trend

increases across a period, decreases down a group

metallic character trend

increases down a group, decreases across a period

exothermic

releases heat, bond forming

endothermic

absorbs heat, bond breaking

average bond enthalpy

energy needed to break 1 mole of a bond in a gaseous molecule averaged over similar compounds

enthalpy change of reaction

enthalpy change when reactants in a stoichiometric equation react to give products under standard conditions

enthalpy change of formation

enthalpy change when 1 mole of a compound is formed from its elements under standard conditions

enthalpy change of combustion

enthalpy change when 1 mole of a substance is burned in excess oxygen

enthalpy change of neutralization

enthalpy change when 1 mole of H2O is formed by reacting an acid and an alkali under standard conditions