Chemical Representations and Empirical Formulas

Dot and Cross Diagrams

Represent electron sharing in covalent bonds.

Ball and Stick Models

3D representation of molecular structures.

Empirical Formula

Simplest ratio of atoms in a compound.

Relative Formula Mass (Mr)

Sum of atomic masses in a chemical formula.

Moles Calculation

Moles = mass / molar mass.

Concentration of Solutions

Measured in grams per dm³.

Avogadro's Constant

6.02 x 10²³ particles per mole.

Limiting Reactant

Reactant that determines product amount formed.

Stoichiometry

Ratios of reactants and products in reactions.

Law of Conservation of Mass

Mass of reactants equals mass of products.

Relative Molecular Mass

Mass of a molecule based on atomic masses.

Chemical Equation Balancing

Equal number of atoms on both sides.

Molecular Formula

Actual number of atoms in a molecule.

Reactants and Products

Substances consumed and formed in a reaction.

Covalent Molecular Limitations

Dot-cross diagrams fail to show electronegativity.

High Melting Points

Characteristic of most metals.

Good Conductors of Electricity

Property of metals due to free electrons.

Mass of Oxygen Calculation

Mass oxygen = mass magnesium oxide - mass magnesium.

Moles of Magnesium

Calculated using mass and molar mass.

Molecular Formula from Empirical

Multiply empirical formula by a whole number.

Chemical Reaction in Closed System

Mass remains constant during precipitation reactions.

Chemical Reaction in Open System

Mass changes due to gas loss or gain.

Calculating Masses from Balanced Equations

Use moles and molar mass for conversions.

Mass of Solute Calculation

Mass = concentration x volume.

3D Arrangement of Atoms

Not shown in 2D diagrams.

Heat Magnesium Experiment

Determines empirical formula of magnesium oxide.

Simplified Empirical Formula

Lowest whole number ratio of elements.