Chemistry Study Guide: Units, Atomic Structure, and Stoichiometry

Comprehensive vocabulary flashcards covering key terms, units, periodic trends, naming rules, and stoichiometry concepts from Chemistry Chapters 1 through 3.

Chemistry

The study of matter and energy and the changes that they undergo.

SI Base Units

The standard base units of measurement, including meter ($\text{m}$) for length, kilogram ($\text{kg}$) for mass, second ($\text{s}$) for time, Kelvin ($\text{K}$) for temperature, mole ($\text{mol}$) for number of particles, ampere ($\text{A}$) for electric current, and candela ($\text{cd}$) for luminous intensity.

Derived Unit

A unit produced by combining base units through multiplication or division, such as volume ($\text{m}^3$) or energy (Joule, $\text{J} = \text{kg}\,\text{m}^2\,\text{s}^{-2}$).

Dimensional Analysis

A problem-solving technique where units are used as a guide to establish conversion factors and find the final solution.

Accuracy

How close measured values are to the true value of a known standard.

Precision

The reproducibility of measurements, or how close repeated measurements are to each other.

Random Error

Inconsistent measurement error occurring by chance that impacts precision and can be reduced by averaging multiple repeated measurements.

Systematic Error

Inherent instrumental error that remains constant across measurements, impacts accuracy, and can be corrected through calibration.

Exact Numbers

Values with no uncertainty that do not limit significant figure calculations, such as counted objects or defined unit conversions.

Density

An intensive property representing the ratio of an object's mass to its volume ($d = \frac{m}{V}$).

Intensive Property

A property of matter that does not depend on the amount of substance present, such as density or temperature.

Extensive Property

A property of matter that depends directly on the amount of substance present, such as mass or volume.

Proton

A positively charged subatomic particle in the nucleus with a charge of $+1.602 \times 10^{-19}\,\text{C}$ ($+1$ relative) and an actual mass of $1.673 \times 10^{-27}\,\text{g}$.

Electron

A negatively charged subatomic particle outside the nucleus with a charge of $-1.602 \times 10^{-19}\,\text{C}$ ($-1$ relative) and an actual mass of $9.109 \times 10^{-31}\,\text{g}$.

Neutron

An uncharged subatomic particle in the nucleus with a charge of $0$ and an actual mass of $1.675 \times 10^{-27}\,\text{g}$.

Nucleons

The fundamental subatomic particles located within the nucleus, specifically protons and neutrons.

Cation

A positively charged ion formed when an atom loses electrons, resulting in more protons than electrons ($\#p^+ > \#e^-$).

Anion

A negatively charged ion formed when an atom gains electrons, resulting in fewer protons than electrons ($\#p^+ < \#e^-$).

Atomic Number ($Z$)

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

Mass Number ($A$)

The total count of nucleons (protons plus neutrons) in the nucleus of an atom.

Isotopes

Atoms of the same element containing identical numbers of protons but different numbers of neutrons, giving them distinct mass numbers.

Atomic Mass Unit (amu)

A relative mass unit defined as exactly $\frac{1}{12}$ the mass of a single carbon-12 atom.

Atomic Weight

The weighted average mass of all naturally occurring isotopes of an element based on their fractional abundances.

Metals

Elements characterized by lustre, malleability, ductility, and good heat and electrical conductivity, which tend to lose electrons to form cations.

Non-Metals

Elements characterized by a dull, brittle appearance and insulating properties, which tend to gain electrons to form anions.

Semimetals (Metalloids)

Elements possessing properties intermediate between metals and non-metals, specifically B, Si, Ge, As, Sb, Te, and At.

Alkali Metals

Group 1 elements that readily lose one electron to form cations with a $+1$ charge and exhibit high reactivity.

Alkaline Earth Metals

Group 2 elements that form cations with a $2+$ charge and are moderately reactive.

Chalcogens

Group 16 elements, also called the oxygen family, which tend to gain two electrons to form anions with a $-2$ charge.

Halogens

Group 17 reactive non-metals that form diatomic molecules in their standard state and form anions with a $-1$ charge.

Noble Gases

Group 18 elements that are chemically unreactive and stable.

Molecule

A distinct, electrically neutral assembly consisting of a specific number of non-metal atoms bound together.

Ionic Compound

A neutral compound composed of oppositely charged cations and anions arranged in a crystal lattice, usually consisting of a metal and a non-metal.

Oxyanions

Polyatomic anions containing oxygen, named with systematically defined prefixes and suffixes like hypo-, -ite, -ate, and per- depending on oxygen count.

Diatomic Elements

Seven elements that exist naturally as two-atom molecules in their standard state: $H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

Physical Change

A change that alters physical properties or state of matter without changing its core chemical composition.

Chemical Change

A process where atomic bonds are broken and formed, rearranging atoms to yield new chemical substances.

Aqueous State ($aq$)

A state symbol indicating that a substance is dissolved in water.

Mole

An SI base unit representing the amount of substance containing Avogadro's number ($N_A = 6.022 \times 10^{23}$) of particles, defined by the number of atoms in $12\,\text{g}$ of carbon-12.

Molar Mass

The mass in grams of one mole of a substance ($\text{g\,mol}^{-1}$), numerically equal to its formula mass in atomic mass units.

Limiting Reagent

The reactant in a chemical reaction that is completely consumed first, determining the maximum amount of product formed.

Excess Reagent

The reactant that remains in unreacted surplus after the limiting reagent is fully consumed.

Theoretical Yield

The maximum calculated quantity of product obtainable from a reaction based on balanced stoichiometric relationships.

Actual Yield

The actual amount of product isolated experimentally from a reaction performed in a laboratory.

Percent Yield

The ratio of actual yield to theoretical yield expressed as a percentage: $\%\text{ yield} = \left(\frac{\text{actual yield}}{\text{theoretical yield}}\right) \times 100$.

Solution

A homogeneous mixture created when a solute is completely dissolved in a solvent.

Strong Electrolyte

A solute that completely dissociates into ions in aqueous solution and conducts electricity strongly.

Weak Electrolyte

A solute that only partially dissociates into ions in aqueous solution and conducts electricity weakly.

Nonelectrolyte

A molecular substance that dissolves in water without forming ions and does not conduct electricity.

Acid-Base Neutralization

A chemical reaction in which an acid reacts with a base to produce a salt and water.

Molarity ($M$)

A unit of solution concentration defined as the moles of solute per liter of solution ($M = \frac{\text{mol solute}}{\text{L sol'n}}$).

Dilution

The process of lowering a solution's concentration by adding solvent, governed by the relation $M_{\text{conc}}V_{\text{conc}} = M_{\text{dil}}V_{\text{dil}}$.

Titration

A volumetric lab technique where a solution of known concentration (titrant) is added to a solution of unknown concentration (analyte) to determine its concentration.

Indicator

A chemical reagent added during a titration that undergoes a physical color change at or near the equivalence point to signal the reaction endpoint.