BackGOB Chemistry: Ionic Compounds, Bonding, Chemical Equations, and Gases – Study Guide
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Ions and Ionic Compounds
Formation and Naming of Ions
Ions are atoms or molecules that have gained or lost electrons, resulting in a net electrical charge. Cations are positively charged (loss of electrons), while anions are negatively charged (gain of electrons).
Symbol and Name for Ions: The symbol for an ion includes the element symbol and its charge (e.g., N3− for nitride, Ca2+ for calcium ion).
Example: An atom with 7 protons and 10 electrons is N3− (nitride ion). An atom with 20 protons and 18 electrons is Ca2+ (calcium ion).
Writing Ionic Formulas
Ionic compounds are formed from the electrostatic attraction between cations and anions. The formula is written to balance the total positive and negative charges.
Example: Lithium (Li+) and Nitrogen (N3−) form Li3N.
Naming Ionic Compounds
The name of an ionic compound consists of the cation name followed by the anion name (with the anion ending in -ide).
Example: Mg3N2 is named magnesium nitride.
Common Polyatomic Ions and Compounds
Some ions consist of multiple atoms (polyatomic ions), such as NO2− (nitrite) and ClO3− (chlorate).
Examples:
Cu(NO2)2: Copper (II) nitrite
KClO3: Potassium chlorate
Chemical Bonding and Lewis Structures
Lewis Structures
Lewis structures represent the arrangement of valence electrons in molecules. Dots represent electrons, and lines represent bonds.
Example: The Lewis structure for Cl2O is:
Cl–O–Cl, with lone pairs on each atom.
Electronegativity and Bond Polarity
Electronegativity is the ability of an atom to attract electrons in a bond. The difference in electronegativity determines bond type:
Nonpolar Covalent: Electrons shared equally (e.g., Br–Br).
Polar Covalent: Electrons shared unequally (e.g., P–Cl).
Ionic: Electrons transferred (e.g., Na–O).
Dipole direction is from δ+ (less electronegative) to δ− (more electronegative).
VSEPR Theory and Molecular Shape
Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular shapes based on electron pair repulsion around a central atom.
Example: SiCl4 has a tetrahedral shape.
Chemical Equations and Stoichiometry
Balancing Chemical Equations
Balanced equations have equal numbers of each atom on both sides. Coefficients are used to balance atoms.
Example: Na3PO4(aq) + MgCl2(aq) → Mg3(PO4)2(s) + NaCl(aq)
Counting Atoms in Equations
To count atoms, multiply the coefficient by the subscript for each element.
Example: In 2FeCl3, there are 2 × 1 = 2 Fe atoms and 2 × 3 = 6 Cl atoms.
Stoichiometry and Mole Calculations
Stoichiometry involves using balanced equations to calculate amounts of reactants or products.
Mole-to-Mole Relationships: Use coefficients from balanced equations to relate moles of substances.
Example: 2Fe(s) + 3S(s) → Fe2S3(s): 2 moles Fe react with 3 moles S.
Molar Mass and Mass Calculations
Molar mass (g/mol) is used to convert between moles and grams.
Formula:
Example: 0.750 mol Ag × 107.87 g/mol = 80.9 g Ag
Gases and Gas Laws
Gas Pressure and Units
Gas pressure can be measured in mmHg, atm, or other units. Conversion: 1 atm = 760 mmHg.
Formula:
Example: 4820 mmHg = 6.34 atm
Gas Laws
Gas laws describe the relationships between pressure, volume, temperature, and amount of gas.
Boyle's Law: (at constant T and n)
Charles's Law: (at constant P and n)
Combined Gas Law:
Partial Pressure and Dalton's Law
The total pressure of a gas mixture is the sum of the partial pressures of each component.
Formula:
Example: If total pressure is 7.00 atm and O2 is 1140 mmHg (1.50 atm), then He = 7.00 – 1.50 = 5.50 atm.
Selected Table: Common Polyatomic Ions and Their Names
Formula | Name |
|---|---|
NO2− | Nitrite |
ClO3− | Chlorate |
PO43− | Phosphate |
SO42− | Sulfate |
CO32− | Carbonate |
NH4+ | Ammonium |
Additional info:
Some explanations and examples were expanded for clarity and completeness.
Table of common polyatomic ions was inferred for context.
