Chemistry Finals Study Guide

Mass

Total number of protons and neutrons in an atom.

Average atomic mass

Weighted average of the atomic masses of an element's isotopes.

Density

Mass of an object divided by its volume.

Percent error

Calculation that expresses the difference between a measured value and an accepted value.

Frequency

Number of occurrences of a repeating event per unit of time.

Half-life

The time taken for half of the quantity of a radioactive substance to decay.

Law

A statement that explains the relationship between variables and how it happens.

Theory

An explanation that has been tested and is based on observed evidence.

Net ionic equation

An equation that shows only the ions that participate in a chemical reaction.

Spectator ion

An ion that does not participate in the overall reaction but is present in the solution.

Precipitate

A solid that forms from a liquid solution during a chemical reaction.

Amplitude

The maximum extent of a wave measured from its equilibrium position.

Wavelength

The distance between successive crests of a wave.

Quantum

The smallest discrete quantity of any physical property.

Orbital

Regions in space where electrons are likely to be found.

Valence electron

Electrons in the outermost shell of an atom, involved in chemical bonding.

Periodic law

The principle that the properties of elements are a periodic function of their atomic numbers.

Periodic trend

Patterns observed within the periodic table.

Electronegativity

A measure of an atom's ability to attract and hold onto electrons.

Atomic radius

The size of an atom, typically measured as half the distance between two nuclei.

Ionization energy

The energy required to remove an electron from an atom or ion.

Octet rule

Atoms are stable when they have eight electrons in their valence shell.

Hydrate

A compound that contains water molecules within its structure.

Anhydrous

A substance that contains no water.

Polar bond

A bond between two atoms that have different electronegativities.

Nonpolar bond

A bond where two atoms share electrons equally.

Error

The difference between a measured value and the true value.

Precision

The closeness of two or more measurements to each other.

Accuracy

The closeness of a measurement to the true value.

Derived unit

A unit that is derived from the fundamental SI units.

Ion

An atom or molecule that has a net electric charge due to the loss or gain of one or more electrons.

Isotope

Atoms of the same element with different numbers of neutrons.

Chain reaction

A series of reactions where each event causes the next one.

Radioactivity

The process by which unstable atomic nuclei lose energy by emitting radiation.

Nuclear bombardment

A process where particles collide with a nucleus to induce a reaction.

Nuclear decay

The process by which an unstable atomic nucleus loses energy.

Nuclear fission

The splitting of a heavy nucleus into smaller nuclei, releasing energy.

Nuclear fusion

The combining of two light atomic nuclei to form a heavier nucleus, releasing energy.

Chemical reaction

A process in which substances combine or break apart to form new substances.

JJ. Thomson

Discovered electrons and proposed the 'plum pudding model' of the atom.

E. Rutherford

Proposed that protons are in the nucleus and electrons revolve around it.

Bohr

Introduced the idea that electrons occupy quantized energy levels.

Dalton’s atomic theory

A theory that states that atoms can't be divided, all atoms of an element are identical, and compounds are formed in whole-number ratios.

Physical change

A change that alters a substance without changing its composition.

Chemical change

A change that results in a new substance formed with different properties.

Alpha particle

A positively charged particle consisting of two protons and two neutrons.

Beta particle

A high-speed electron or positron emitted in the radioactive decay of an atomic nucleus.

Gamma ray

A high-energy electromagnetic radiation emitted by radioactive decay.

Heisenberg uncertainty principle

It is impossible to simultaneously know the exact position and momentum of a particle.

Pauli exclusion principle

No two electrons in an atom can have the same four quantum numbers.

Alkali metals

Highly reactive metals in group 1 of the periodic table.

Noble gases

Inert gases located in group 18 of the periodic table that have full valence shells.

Metalloids

Elements that have properties intermediate between metals and nonmetals.

Covalent compounds

Compounds formed by the sharing of electron pairs between atoms.

Ionic compounds

Compounds formed by the transfer of electrons from one atom to another.