Atoms, Elements, and Compounds Lecture Review

Flashcards covering key vocabulary related to atoms, elements, compounds, properties of matter, and the periodic table, derived from lecture notes.

Intensive Property

A property that does not depend on the amount of matter present (e.g., boiling point, temperature, freezing point, density).

Extensive Property

A property that depends on the amount of matter present (e.g., mass, volume).

Physical Property

A characteristic of a substance that can be observed or measured without changing the substance's chemical identity (e.g., mass, volume, density).

Chemical Property

A characteristic of a substance that describes its ability to undergo a chemical change (e.g., flammability/combustion).

Physical Change

A change in the form or appearance of a substance, but not its chemical identity (e.g., sugar dissolving in water, water evaporating, rock pulverizing).

Mixture

A substance composed of two or more substances that are not chemically combined.

Metal

Elements generally found on the left and center of the periodic table, typically lustrous, good conductors of heat and electricity, and malleable (e.g., K, Na).

Nonmetal

Elements generally found on the upper right side of the periodic table, typically dull, poor conductors, and brittle (e.g., S, N).

Metalloid (Semimetal)

Elements located along the stair-step line on the periodic table, exhibiting properties intermediate between metals and nonmetals (e.g., B, Si, Ge, Sb, Te).

Diatomic Element

Elements that naturally exist as molecules composed of two atoms (e.g., H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂).

Halogen

Elements in Group 17 (VIIA) of the periodic table, highly reactive nonmetals (e.g., F, Cl, Br, I).

Alkali Metal

Elements in Group 1 (IA) of the periodic table (excluding hydrogen), highly reactive metals (e.g., Li, Na, K, Rb, Cs, Fr).

Proton (p+)

A positively charged subatomic particle found in the nucleus of an atom; defines the element's atomic number.

Electron (e-)

A negatively charged subatomic particle that orbits the nucleus of an atom. In a neutral atom, the number of electrons equals the number of protons.

Neutron (n°)

A neutral subatomic particle found in the nucleus of an atom.

Atomic Number

The number of protons in the nucleus of an atom, which uniquely identifies an element.

Mass Number (A)

The total number of protons and neutrons in the nucleus of an atom, defining a specific isotope.

Ion

An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons, leading to different mass numbers.

Atomic Mass (Weighted Average)

The average mass of all naturally occurring isotopes of an element, weighted by their isotopic abundances.

Isotopic Abundance

The relative proportion of a particular isotope in a naturally occurring sample of an element.

Period (Periodic Table)

A horizontal row in the periodic table, indicating the number of electron shells (e.g., periods 2 and 3 have 8 elements; periods 4 and 5 have 18 elements).