Chemistry Review: Atomic Structure, Periodic Trends, and Matter

Vocabulary practice flashcards covering fundamental chemistry topics including atomic structure, isotopes, periodic trends, chemical vs. physical properties, and element classifications.

Neutron

A subatomic particle located in the nucleus that carries no electric charge.

Ernest Rutherford

The scientist credited with discovering the atomic nucleus through the gold foil experiment.

Mass Number

The total number of protons and neutrons in an atom's nucleus (e.g., an atom with 17 protons and 18 neutrons has a mass number of 35).

Isotopes

Atoms of the same element that have the same number of protons but a different number of neutrons.

Average Atomic Mass

The weighted average mass of an element's naturally occurring isotopes, calculated using the formula: $\sum (\text{mass} \times \text{fractional abundance})$.

Groups (or Families)

The vertical columns of elements on the periodic table.

Nonmetal

An element that is typically a poor conductor of heat and electricity and tends to gain electrons in chemical reactions.

Compound

A substance composed of two or more elements chemically combined in a fixed ratio.

Heterogeneous Mixture

A mixture with a non-uniform composition where individual components remain visibly distinct, such as a salad with visible vegetable pieces.

Liquid

A state of matter that possesses a definite volume but an indefinite shape.

Chemical Property

A characteristic of a substance that describes its ability to undergo a chemical change, such as flammability.

Physical Change

A change in the physical state or appearance of a substance that does not alter its chemical composition, such as ice melting into water.

Chemical Reaction

A process in which chemical bonds are broken and formed so that atoms are rearranged rather than created or destroyed.

Scientific Law

A concise statement summarizing what has been observed to happen consistently in nature.

Atomic Number

The number of protons in an atom, which dictates the modern periodic table's ordering and is written as the subscript in isotope notation.

Valence Electrons

The electrons in the outermost energy level of an atom (for example, sulfur in Group 16 contains 6 valence electrons).

Nitrogen Electron Configuration

The noble gas shorthand notation for nitrogen: $[\text{He}]2s^2 2p^3$.

Atomic Radius Trend (Across a Period)

The general decrease in atomic size from left to right across a period caused by increasing nuclear charge pulling electrons closer to the nucleus.

Ionization Energy Trend (Down a Group)

The general decrease in the energy required to remove a valence electron when moving down a group because valence electrons are farther from the nucleus.

Electronegativity

An atom's tendency to attract electrons when forming a chemical bond.

Alkali Metals

The highly reactive metallic elements located in Group 1 of the periodic table, excluding hydrogen.

Alkaline Earth Metals

The metallic elements located in Group 2 of the periodic table that typically lose two electrons to form ions with a $2+$ charge.

Metalloid

An element located along the 'staircase' dividing line of the periodic table (such as silicon, $\text{Si}$) possessing properties intermediate between metals and nonmetals.

Periods

The horizontal rows of elements on the periodic table.

Halogens

The nonmetallic elements in Group 17 of the periodic table that typically gain one electron to form ions with a $1-$ charge.