Atomic Structure and Peirodicity

Decreases

Atomic Radius across the period

Increases

Atomic radius down groups

Atomic Radius

More protons pull electrons closer; more shells add distances

Increase

Ionization Energy across the period

Decrease

Ionization down group

Ionization Energy

Harder to remove electrons as nuclear charge increases.

Increases

Electronegativity across period

Decreases

electronegativity down group

Electronegativity

Atoms more strongly attract electrons to complete octet

Decreases

Metallic Character across period

Increases

Metallic character down group

Metallic Character

Metals lose electrons easily; trend mirrors metal reactivity.

Synthesis

Two or more reactant combine to form one product (2H₂+O₂ —> 2H₂O)

Decomposition

A single compound breaks into simpler substances (2KCIO₃ —> 2KCI + 3O₂)

Single Replacement

One element replaces another in a compound (Zn + CuSO₄ —> ZnSO₄ + Cu)

Double Replacement

Ions in two compounds switch partners (AgNO₃ + NaCl —> AgCl + NaNO₃

Combustion

Hydrocarbon + O₂ —> CO₂ + H₂O; always exothermic (CH₄ + 2O₂ —> CO₂ + H₂O)

Acid-Base

Acid + base —> water + salt (HCl + NaOH —> NaCl + H₂O)

Mole-to-Mole Conversion

Use mole ratios from balanced equation

Mass-to-Mass Calculation

Convert grams to moles —> use mole ratio —> convert back to grams

Limiting Reactant Problems

Determine which reactant runs out first by comparing mole availability

Theoretical Yield

Maximum product formed from limiting reactant

Percent Yield

(Actual Yield / Theoretical Yield) x 100

Enthalpy

△H Heat change at constant pressure △H < 0 (exothermic)

Entropy

△S Disorder of randomness △S > 0 (Increased disorder)

Gibbs Free Energy

△G △G = △H - T△S △G < 0

Concentration of Reactant

Higher concentration increases collision frequencies

Temperature

Increased temperature raise kinetic energy, leading to more effective collisions.

Catalyst

Lower the activation energy (Ea) and speed up the reaction without being consumed

Surface Area

More surface area in solids increases collision opportunities

Molarity (M)

Moles of solute per liter of solution (1.0 M NaCl = 1 mole CaCl in 1 L)

Molality (m)

Moles of solute per kilogram of solvent (Used in boiling/freezing point problems)

Percent by Mass

(Mass of solute / Mass of solution) x 100 (common in pharmacy contexts)

Mole Fraction

Moles of Solute / Total moles in solution (Used in vapor pressure calaculation)

Shift right

Adding reactant

Shift right

removing products

shift right

Increasing temperature of endothermic reactions

shift left

Increasing temperature of exothermic reactions

Shift toward fewer moles of gas

Increasing pressure (decreasing volume)

No effect on equilibrium position

Adding a catalyst: increases rate of both forward and reverse reactions equally