Chemical Bonds, Reactions, and Gas Laws Overview

Electronegativity

Electronegativity is the tendency of an atom to attract a shared pair of electrons toward itself in a chemical bond. The greater the electronegativity, the stronger the atom's pull on electrons.

Type of bond using electronegativity difference

Subtract the smaller electronegativity from the larger: If the difference is >1.7, the bond is ionic (electrons are transferred). If the difference is between 0.4 and 1.7, the bond is polar covalent (unequal sharing). If the difference is <0.4, the bond is nonpolar covalent (equal sharing).

Nonpolar covalent bond

A bond where two atoms share electrons equally because their electronegativities are similar. Typically occurs between identical atoms.

Polar covalent bond

A bond where electrons are shared unequally between atoms, resulting in partial positive and negative charges on the atoms.

Ionic bond

A chemical bond formed when one atom donates an electron to another, resulting in a bond between positively and negatively charged ions.

Properties of ionic compounds

Crystalline solids, high melting and boiling points, conduct electricity when dissolved in water, and are usually soluble in water.

Formula of Sodium sulfide

Na2S — Sodium (Na+) and Sulfide (S2-) combine in a 2:1 ratio to balance charges.

Compound Mg2N3

Magnesium nitride — formed from Mg3+ and N3- ions in a 3:2 ratio.

Ammonium

NH4+

Hydroxide

OH-

Nitrate

NO3-

Sulfate

SO4^2-

Acetate

C2H3O2-

Chlorate

ClO3-

Carbonate

CO3^2-

Phosphate

PO4^3-

Molecular compound NCl3

Nitrogen trichloride — composed of 1 nitrogen and 3 chlorine atoms.

Lewis structure

A diagram that shows the bonding between atoms in a molecule and the lone pairs of electrons that may exist.

VSEPR

Valence Shell Electron Pair Repulsion theory — used to predict molecular geometry by minimizing electron pair repulsion.

Main VSEPR shapes

Linear (2 bonds), Bent (2 bonds, 1 or 2 lone pairs), Trigonal planar (3 bonds), Trigonal pyramidal (3 bonds, 1 lone pair), Tetrahedral (4 bonds).

Polar molecule

A molecule that has a net dipole moment due to the presence of polar bonds that do not cancel out.

Polar Molecule

A molecule is polar if it has polar bonds and the molecular geometry causes an uneven distribution of charge.

London Dispersion

Weak attractions in all molecules due to temporary dipoles.

Dipole-Dipole

Attractions between polar molecules.

Hydrogen Bonds

Strong dipole interactions between H and N, O, or F.

Signs of a Chemical Reaction

Color change, temperature change, formation of a gas, formation of a precipitate, and light or sound.

Balanced Chemical Equation

An equation that shows the same number of each atom on both sides, reflecting conservation of mass.

Synthesis Reaction

A + B → AB

Decomposition Reaction

AB → A + B

Single Replacement Reaction

A + BC → AC + B

Double Replacement Reaction

AB + CD → AD + CB

Combustion Reaction

Hydrocarbon + O2 → CO2 + H2O

Mole Ratio

A conversion factor from a balanced equation that shows the ratio of moles of reactants to products.

Limiting Reactant

The reactant that is completely consumed first, limiting the amount of product formed.

Percent Yield

(Actual yield / Theoretical yield) x 100. It tells how efficient the reaction was.

Pressure and Temperature Relationship

Pressure increases due to increased kinetic energy and particle collisions when temperature increases (at constant volume).

Pressure and Volume Relationship

Pressure increases because particles collide more frequently in a smaller space when volume decreases (at constant temperature).

Conversion of Torr to atm

888 torr ÷ 760 = 1.17 atm

Conversion of Celsius to Kelvin

55 + 273 = 328 K

Ideal Gas Law

PV = nRT, where P = pressure, V = volume, n = moles, R = gas constant, T = temperature (Kelvin).

Dalton's Law of Partial Pressures

The total pressure of a gas mixture equals the sum of the partial pressures of individual gases.

Kinetic Molecular Theory Assumptions

Gases are made of tiny particles with negligible volume; particles move in straight lines until they collide; collisions are elastic (no energy lost); no intermolecular forces between gas particles; average kinetic energy is proportional to temperature.

Real Gases vs Ideal Gases

Real gases have volume and intermolecular forces, so they deviate from ideal behavior at high pressure and low temperature.