Atomic Structure and Ions

Atomic Number, Mass Number, and Ions

Atoms are composed of protons, neutrons, and electrons. The atomic number is the number of protons, and the mass number is the sum of protons and neutrons. Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge.

• Cation: An ion with a positive charge (fewer electrons than protons).

• Anion: An ion with a negative charge (more electrons than protons).

• Example: An atom with 13 protons and 10 electrons has a charge of (Al3+).

Chemical Bonding

Ionic and Covalent Bonds

Chemical bonds form when atoms share or transfer electrons to achieve stable electron configurations.

• Ionic Bond: Formed by the transfer of electrons from a metal to a nonmetal, resulting in oppositely charged ions that attract each other (e.g., NaCl).

• Covalent Bond: Formed by the sharing of electrons between two nonmetals (e.g., H2O).

• Polar Covalent Bond: Unequal sharing of electrons due to differences in electronegativity.

• Nonpolar Covalent Bond: Equal sharing of electrons.

Lewis Structures and Molecular Shapes

Lewis structures represent the arrangement of electrons in molecules. The shape of a molecule is determined by the number of electron groups around the central atom (VSEPR theory).

• Bent: 2 bonding pairs and 1 or 2 lone pairs (e.g., H2O, SO2).

• Trigonal Planar: 3 electron groups, 120° bond angles (e.g., BF3).

• Tetrahedral: 4 electron groups, 109.5° bond angles (e.g., CH4).

• Trigonal Pyramidal: 3 bonding pairs, 1 lone pair (e.g., NH3).

Nomenclature and Chemical Formulas

Naming Ionic and Covalent Compounds

• Ionic Compounds: Name the cation (metal) first, then the anion (nonmetal) with an -ide ending (e.g., NaCl: sodium chloride).

• Transition Metals: Use Roman numerals to indicate the charge (e.g., FeCl2: iron(II) chloride).

• Covalent Compounds: Use prefixes to indicate the number of atoms (e.g., CO2: carbon dioxide).

• Polyatomic Ions: Memorize common ions (e.g., SO42-: sulfate, NO3-: nitrate).

Periodic Table and Element Classification

Metals, Nonmetals, and Metalloids

• Metals: Good conductors, malleable, ductile, shiny (e.g., Na, Fe).

• Nonmetals: Poor conductors, brittle, dull (e.g., O, Cl).

• Metalloids: Properties intermediate between metals and nonmetals (e.g., Si, B).

Chemical Equations and Stoichiometry

Balancing Chemical Equations

To balance a chemical equation, ensure the number of atoms of each element is the same on both sides.

• Example:

• Stoichiometry: Use coefficients to relate moles of reactants and products.

Gases and Gas Laws

Gas Laws

• Boyle's Law: (at constant T and n)

• Charles's Law: (at constant P and n)

• Ideal Gas Law:

• Dalton's Law of Partial Pressures:

Standard Pressure Units:

• 1 atm = 760 mmHg = 760 torr = 101,325 Pa = 14.7 psi

Solutions and Concentrations

Types of Solutions and Solubility

• Solute: Substance dissolved in a solvent.

• Solvent: Substance that dissolves the solute (usually present in greater amount).

• Saturated Solution: Contains the maximum amount of solute that can dissolve at a given temperature.

Concentration Units

• Mass/Volume Percent:

• Molarity (M):

Sample Calculations and Applications

• Finding the charge of an ion: Subtract the number of electrons from the number of protons.

• Balancing equations: Adjust coefficients to balance atoms on both sides.

• Gas law problems: Use the appropriate law based on given variables (e.g., Boyle's for pressure/volume changes).

• Solution concentration: Calculate using mass, volume, or molarity formulas.

Additional info:

• Periodic table and polyatomic ion tables are provided for reference and should be memorized for quick recall during exams.

• Understanding molecular geometry is essential for predicting physical and chemical properties of compounds.