General Chemistry & Atomic Theory Vocabulary

Vocabulary flashcards covering SI base units, properties of matter, elemental families, atomic models, forms of energy, and solutions based on introductory chemistry notes.

Significant figures

Numbers that tell information about the precision of a measurement.

Exact numbers

Numbers that do not express a measurement (such as counting or pre-defined numbers), meaning significant figures are not applicable.

Law of definite proportions

States that a compound always contains the same proportion of its component elements.

Law of constant composition

States that all samples of a given compound have the same elemental composition.

Law of multiple proportions

States that when two masses of one element react with a given mass of another element to form two compounds, the two masses of the first element have a ratio of two small whole numbers.

Mass

The quantity of matter.

Matter

Anything that has mass and occupies space.

Pure substance

Matter that has a constant composition and cannot be broken down into simpler matter by any physical process.

Physical process

A transformation of a sample of matter that does not alter the chemical identity of the substance.

Physical properties

Properties of a substance that can be observed without changing the substance into another.

Extensive properties

Properties that vary with the amount of substance present.

Intensive property

A property that is independent of the amount of the substance.

Chemical properties

Properties of a substance that can be observed only by reacting the substance with something else to form a new substance.

Chemical reaction

A conversion of one or more substances into one or more different substances.

Immiscible liquids

Combinations of liquids that do not mix with, or dissolve in, each other.

Distillation

A technique using evaporation and condensation to separate a mixture of substances with different boiling points.

Filtration

A technique for separating solid particles from a liquid.

Sublimation

The transformation of a solid directly into a gas.

Deposition

The transformation of a gas directly into a solid.

Molecular formula

Indicates how many atoms of each element are in one molecule of a pure substance.

Molecule

A collection of atoms held together by chemical bonds.

Structural formula

A representation of a molecule that uses short lines between the symbols of elements to show chemical bonds between atoms.

Ball-and-stick models

3-dimensional representations of molecules.

Space-filling models

A more accurate 3D representation of molecules where seeing all atoms and bond angles is difficult.

Ionic compounds

A compound that consists of a characteristic ratio of positive and negative ions.

Empirical formula

A chemical formula in which subscripts represent the simplest whole-number ratio of the atoms or ions in a compound.

Energy

The capacity to do work ($w$).

Work

Accomplished by moving an object over a distance.

Kinetic energy

The energy of an object in motion because of its mass ($m$) and its speed ($u$), calculated as $KE = \frac{1}{2} m u^2$.

Potential energy

The energy stored in an object because of its position or composition, calculated as $PE = \frac{k Q_1 Q_2}{d}$.

Heat

The transfer of energy between objects that occurs because of differences in their temperatures.

Law of conservation of energy

States that energy cannot be created nor destroyed.

Absolute zero ($0\,\text{K}$)

The zero point on the Kelvin temperature scale; theoretically the lowest temperature possible and the point at which particles have zero kinetic energy.

Unit conversion factor

A fraction in which the numerator is equivalent to the denominator but expressed in different units.

Alkali metals

Elements categorized in Group 1 of the periodic table.

Alkaline earth metals

Elements categorized in Group 2 of the periodic table.

Chalcogens

Elements categorized in Group 16 of the periodic table.

Halogens

Elements categorized in Group 17 of the periodic table.

Noble Gases

Elements categorized in Group 18 of the periodic table.

Cathode rays

Streams of electrons emitted by the cathode in a partially evacuated tube.

The Billiard Ball Model

John Dalton's atomic model describing atoms as solid, indivisible, indestructible spheres that combine in fixed whole-number ratios to form compounds.

The Plum Pudding Model

J.J. Thomson's atomic model seeing atoms as having no electric charge, with a balance of positive and negative charge (positive charge spread out).

The Rutherford Planetary Model

Atomic model that develops the nucleus as a concentrated center of charged positive energy.

Radioactivity

The spontaneous emission of high-energy radiation or particles by materials.

Beta particles

A particle emitted during radioactive decay that is equivalent in mass and charge to a high-energy electron.

Alpha particles

A particle emitted during radioactive decay that is equivalent in mass and charge to a ${}^4\text{He}$ nucleus.

Proton

A subatomic particle in the nucleus that has a positive charge and a mass number of one.

Neutron

An electrically neutral subatomic particle with a mass number of one.

Avogadro's number

The constant $6.0221367 \times 10^{23}$, which defines the number of particles in $1\,\text{mol}$.

Solution

A mixture that is well-mixed at the atomic or molecular level (homogeneous).

Aqueous Solution

A solution with $\text{H}_2\text{O}$ as the solvent.

Molar concentration

Also known as Molarity ($M$), defined as $\frac{\text{moles of solute}}{\text{liter of solution}}$.