Chemistry Final Exam

Atom

The smallest unit of matter, composed of protons, neutrons, and electrons. Atoms form elements.

Element

Defined by the number of protons in its atoms (atomic number). All atoms of an element have the same number of protons.

Isotope

Atoms of the same element with different numbers of neutrons. Same atomic number, different mass numbers.

Ion

An atom that has gained or lost electrons, becoming charged.

Cation

A positive ion that has lost electrons.

Anion

A negative ion that has gained electrons.

Valence Electrons

Electrons in the outermost shell of an atom that determine bonding and reactivity.

Atomic Number

The number of protons in an atom.

Atomic Mass

The weighted average of all isotopes (protons + neutrons).

Periods (in the periodic table)

Horizontal rows that indicate the same number of electron shells.

Groups (in the periodic table)

Vertical columns that indicate the same number of valence electrons and similar properties.

Ionic Bond

A bond formed by the transfer of electrons between a metal and a nonmetal.

Covalent Bond

A bond formed by the sharing of electrons between nonmetals.

Metallic Bond

A bond characterized by a sea of electrons among metal atoms.

Naming Ionic Compounds

Name the metal first, then the nonmetal with ‘-ide’. Use Roman numerals for transition metals.

Naming Covalent Compounds

Use prefixes (mono-, di-, tri-) for both elements.

Chemical Formula

A representation of a compound where ion charges are balanced; total charges must cancel out.

Formula Mass Calculation

Add the atomic masses of all atoms in a compound using the periodic table.

Balancing Chemical Equations

1. Count atoms on both sides. 2. Use coefficients to balance. 3. Never change subscripts. 4. Check your work.

pH Scale

Measures concentration of H⁺ ions: 0–6 acidic, 7 neutral, 8–14 basic (alkaline).

Molarity

Moles of solute per liter of solution; Formula: M = mol/L.

Saturated Solution

A solution that holds the maximum amount of solute.

Unsaturated Solution

A solution that can dissolve more solute.

Supersaturated Solution

A solution that holds more solute than normal (unstable).

Solution

A homogeneous mixture with uniform composition.

Suspension

A heterogeneous mixture where particles settle out.

Mixture

A combination of substances that are not chemically bonded.

Lewis Structure

A diagram showing valence electrons and bonds between atoms using dots and lines.

Polar Molecule

A molecule with unequal electron sharing, resulting in a dipole (e.g., H₂O).

Non-polar Molecule

A molecule with equal electron sharing (e.g., O₂).

Energy Sublevels

Regions within an atom's shell where electrons are likely to be found: s, p, d, f with varying number of orbitals.

Radioactivity

The spontaneous emission of radiation by an unstable atomic nucleus.

Alpha Radiation

Radiation consisting of 2 protons and 2 neutrons; blocked by paper.

Beta Radiation

Radiation in the form of electrons; blocked by aluminum.

Gamma Radiation

High-energy electromagnetic radiation; requires lead to block.

Nuclear Fission

The process of splitting a nucleus (e.g., uranium in reactors).

Nuclear Fusion

The process of combining nuclei (e.g., in the sun).

Nuclear Transmutation

When one element changes into another due to a nuclear reaction (e.g., radioactive decay).

Exothermic Reaction

A reaction that releases energy and feels hot.

Endothermic Reaction

A reaction that absorbs energy and feels cold.

Catalyst

A substance that speeds up a chemical reaction without being consumed.