Chemistry
Chemistry
Atomic structure, bonding, reactions, equilibrium, and organic chemistry — complete chemistry cheatsheet.
01Atomic Structure▼
Proton
Positive charge, mass 1. In nucleus.
Neutron
No charge, mass 1. In nucleus.
Electron
Negative charge, mass 1/1836. In shells.
Atomic number
= protons = electrons (neutral atom)
Mass number
= protons + neutrons
Isotopes
Same protons, different neutrons. Same element, different mass.
CHEMElectron configuration
First 20 elements: 2,8,8,2 pattern after H and He Shells: 1(max 2), 2(max 8), 3(max 8 first) Na: 2,8,1. Cl: 2,8,7. Ca: 2,8,8,2 Ions: Na+ loses 1e-, Cl- gains 1e-
02Chemical Bonding▼
| Bond type | Between | Strength | Example |
|---|---|---|---|
| Ionic | Metal+nonmetal | Strong (in lattice) | NaCl, MgO |
| Covalent | Nonmetals | Moderate | H2O, CH4 |
| Metallic | Metals | Strong | Fe, Cu, Al |
| H-bond | N/O/F with H | Weak-moderate | Water, DNA |
| Van der Waals | All molecules | Very weak | Noble gases |
💡
Ionic bonds: electron TRANSFER (full charges). Covalent: electron SHARING. Ionic solids: high mp, conduct when molten.
03Reactions & Equations▼
CHEMBalancing equations
Mg + O2 -> MgO (unbalanced) 2Mg + O2 -> 2MgO (balanced) Mole calculations: n = m/Mr (moles = mass/molar mass) n = c x V (moles = concentration x volume in dm3) PV = nRT (ideal gas) Yield: actual/theoretical x 100%
Oxidation
Loss of electrons. Increase in oxidation number.
Reduction
Gain of electrons. Decrease in oxidation number.
OIL RIG
Oxidation Is Loss. Reduction Is Gain.
Acid+base
Neutralisation: H+ + OH- -> H2O
Exothermic
Energy released. Products lower energy than reactants.
04Equilibrium▼
CHEMLe Chatelier's Principle
If conditions change, equilibrium shifts to oppose the change. Increase concentration of reactant -> shifts RIGHT (more products) Decrease product -> shifts RIGHT Increase temperature -> shifts toward ENDOTHERMIC side Increase pressure -> shifts toward FEWER MOLES of gas Catalyst: no shift in position, just reaches equilibrium FASTER Kc = [products]^powers / [reactants]^powers
❓ Quiz
OIL RIG stands for?
OIL RIG: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
05Organic Chemistry▼
| Homologous series | General formula | Functional group |
|---|---|---|
| Alkane | CnH2n+2 | None (single bonds) |
| Alkene | CnH2n | C=C double bond |
| Alcohol | CnH2n+1OH | -OH (hydroxyl) |
| Carboxylic acid | CnH2n+1COOH | -COOH |
| Ester | R-COO-R' | Ester link |
| Amine | R-NH2 | -NH2 |
CHEMReaction types
Alkane + Cl2 -> substitution (UV light) Alkene + Br2 -> addition (electrophilic addition) Alkene + H2O -> alcohol (hydration) Alcohol -> carboxylic acid (oxidation) Acid + alcohol -> ester + water (esterification)
06Thermodynamics & Rates▼
Enthalpy
DH = H(products) - H(reactants)
Negative=exothermic, Positive=endothermic
Hess's Law
DH(reaction) = sum of DH(steps)
Path independent.
Rate
Rate = k[A]^m[B]^n
k=rate constant, m,n=orders.
Activation energy
Minimum energy for reaction
Catalyst lowers Ea.
CHEMRate factors
Concentration: more particles, more collisions Temperature: more energy, more successful collisions Surface area: more exposed particles Catalyst: provides alternate lower Ea pathway