Unit 1-3 Chemistry Review: Measurement, Matter, Atoms, and Electrons

Flashcards covering key vocabulary terms from Units 1, 2, and 3, including measurement rules, atomic theory, nuclear chemistry, and periodic trends.

Qualitative Observation

Descriptions of a system or substance using words rather than numerical measurements.

Quantitative Observation

Observations that involve numerical measurements and units.

Independent Variable

The variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable.

Dependent Variable

The variable being tested and measured in a scientific experiment; it changes based on the independent variable.

Density

The ratio of the mass of an unknown liquid or object to its volume, calculated as $\text{mass} / \text{volume}$.

Physical Property

A characteristic of a substance that can be observed or measured without changing the sample's composition.

Chemical Property

The ability or inability of a substance to combine with or change into one or more new substances.

Physical Change

A type of change that alters the physical properties of a substance but does not change its composition, such as boiling water.

Chemical Change

A process involving one or more substances changing into new substances, also known as a chemical reaction.

Law of Conservation of Mass

The law stating that mass is neither created nor destroyed during a chemical reaction; it is conserved.

Pure Substance

Matter that has a uniform and unchanging composition, such as elements and compounds.

Mixture

A physical blend of two or more pure substances in any proportion in which each substance retains its individual chemical properties.

Element

A pure substance that cannot be broken down into simpler substances by physical or chemical means.

Compound

A chemical combination of two or more different elements; these can be broken down into simpler substances by chemical means.

Heterogeneous Mixture

A mixture that does not blend smoothly throughout and in which the individual substances remain distinct.

Homogeneous Mixture

A mixture that has constant composition throughout; it always has a single phase.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different mass numbers.

Atomic Number

The whole number on the periodic table that is equal to the number of protons in an atom; in a neutral atom, it is also equal to the number of electrons.

Mass Number

The sum of the number of protons and the number of neutrons in an atom's nucleus.

Fission

The process of splitting large nuclei into smaller nuclei, often releasing neutrons and energy.

Fusion

A nuclear reaction that involves hydrogen nuclei joining together to make helium, releasing the largest amount of energy.

Half-life

The amount of time required for half of a radioactive isotope to decay into atoms of a new element.

Wavelength ($\lambda$)

The distance between equivalent points on a continuous wave, such as from crest to crest.

Frequency ($f$ or $\nu$)

The number of waves that pass a given point per second.

Aufbau Principle

States that each electron occupies the lowest energy orbital available.

Pauli Exclusion Principle

States that a maximum of two electrons can occupy a single atomic orbital, but only if the electrons have opposite spins.

Hund's Rule

States that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals.

Periodic Law

The statement that there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number.

Ionization Energy

The energy required to remove an electron from a gaseous atom.

Electronegativity

The relative ability of an atom to attract electrons in a chemical bond.