Some Basic Concepts of Chemistry - Foundations and Mole Concept

Vocabulary practice flashcards covering fundamental chemistry concepts, matter classification, atomic structure, the iso-family, relative atomic mass, the mole concept, gas laws, density terms, and percentage composition.

Chemistry

The branch of physical science that investigates the composition, structure, properties, and transformations of matter, alongside the thermodynamic and kinetic principles governing the associated energy changes.

Matter

Anything that possesses mass and occupies a definite volume (space), consisting of discrete physical particles such as atoms, molecules, or ions.

Non-Matter

Forms of energy or abstract concepts that do not possess mass and do not occupy physical space, lacking particulate building blocks or chemical structures (e.g., light, heat, sound).

Element

A pure substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means.

Compound

A pure substance formed when two or more different elements combine chemically in a fixed ratio, exhibiting distinct properties that differ from those of its constituent elements.

Mixture

A physical combination of two or more substances present in any proportion where each component retains its chemical identity and properties, separable by physical methods.

Homogeneous Mixture

A mixture possessing uniform composition and properties throughout, existing in a single phase (e.g., salt dissolved in water, brass, bronze).

Heterogeneous Mixture

A mixture possessing non-uniform composition throughout and consisting of more than one distinct physical phase (e.g., sand in water, milk, blood).

Atom

The fundamental, smallest unit of ordinary matter that forms chemical elements, consisting of a dense central nucleus (protons and neutrons) surrounded by orbiting electrons.

Molecule

A group of two or more atoms held together by chemical bonds, representing the smallest particle of a substance that has independent, free existence.

Atomicity

The total number of atoms present in one molecule of an elemental or compound substance.

Homoatomic Molecule

A molecule composed of only one type of atom (e.g., $\text{H}_2$, $\text{N}_2$, $\text{O}_3$, $\text{P}_4$, $\text{S}_8$).

Heteroatomic Molecule

A molecule composed of two or more different types of atoms (e.g., $\text{CO}$, $\text{CO}_2$, $\text{H}_2\text{O}$, $\text{NH}_3$).

Atomic Number ($Z$)

The total number of protons present in the nucleus of an atom, uniquely defining the identity of a chemical element.

Mass Number ($A$)

The total number of nucleons (protons plus neutrons) present in the nucleus of an atom, expressed as $A = Z + n$.

Nucleon

A collective term for a subatomic particle situated in the atomic nucleus, specifically a proton or a neutron.

Isotopes

Atoms of the same element having identical atomic numbers ($Z$) but different mass numbers ($A$) due to a differing number of neutrons.

Isobars

Atoms of different chemical elements that share the same mass number ($A$) but possess different atomic numbers ($Z$).

Isotones

Atoms of different elements that possess the same number of neutrons ($A - Z$) but different numbers of protons.

Isoelectronic Species

Atoms, molecules, or ions that contain the exact same total number of electrons (e.g., $\text{O}^{2-}$, $\text{F}^-$, $\text{Na}^+$, $\text{Mg}^{2+}$).

Isosters

Chemical species that possess both the same total number of atoms and the same total number of electrons (e.g., $\text{N}_2\text{O}$ and $\text{CO}_2$).

Isodiaphers

Nuclides having the same excess of neutrons over protons, represented by an equal value of $n - p = A - 2Z$.

Relative Atomic Mass (R.A.M.)

The dimensionless ratio of the mass of one atom of an element to $\frac{1}{12}$ of the mass of one atom of the carbon-12 ($^{12}\text{C}$) isotope.

Atomic Mass Unit ($\text{amu}$)

A unit of mass defined as exactly $\frac{1}{12}$ of the mass of one atom of carbon-12, equivalent to the mass of one nucleon ($\approx 1.67 \times 10^{-24}\,\text{g}$ or $1.67 \times 10^{-27}\,\text{kg}$).

Average Atomic Mass

The weighted average of the atomic masses of all naturally occurring isotopes of an element, calculated using $M_{\text{avg}} = \frac{\sum M_i x_i}{\sum x_i}$ where $x_i$ represents isotopic percentage abundance.

Molecular Mass

The mass of one single molecule of a substance expressed in $\text{amu}$, calculated as the sum of the atomic masses of all atoms present in that molecule.

Avogadro's Number ($N_A$)

The fundamental constant denoting the number of constituent particles contained in one mole of any substance, defined as $6.022 \times 10^{23}$.

Mole

The SI unit for the amount of substance containing the exact number of elementary entities as there are carbon atoms in exactly $12\,\text{g}$ of pure carbon-12.

Gram Atomic Mass (GAM)

The mass of one mole ($6.022 \times 10^{23}$ atoms) of an element expressed in grams, which is numerically equal to its atomic mass in $\text{amu}$.

Gram Molecular Mass (GMM)

The mass of one mole ($6.022 \times 10^{23}$ molecules) of a substance expressed in grams, which is numerically equal to its molecular mass in $\text{amu}$.

Ideal Gas Equation

The equation of state relating pressure, volume, moles, and temperature for an ideal gas, given by $PV = nRT$.

Universal Gas Constant ($R$)

The proportionality constant in the ideal gas law, possessing values of approximately $0.0821\,\text{L}\,\text{atm}\,\text{mol}^{-1}\,\text{K}^{-1}$ or $8.314\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1}$.

STP (Standard Temperature and Pressure)

Standard reference conditions traditionally specified as $0^\circ\text{C}$ ($273\,\text{K}$) and $1\,\text{atm}$ (where $1\,\text{mol}$ of ideal gas occupies $22.4\,\text{L}$), or under newer IUPAC recommendations as $0^\circ\text{C}$ and $1\,\text{bar}$ (where $1\,\text{mol}$ occupies $22.7\,\text{L}$).

SATP (Standard Ambient Temperature and Pressure)

Reference conditions defined as a temperature of $25^\circ\text{C}$ ($298\,\text{K}$) and a pressure of $1\,\text{bar}$ (or $1\,\text{atm}$ in older standards).

Absolute Density

The mass of a substance per unit volume ($\rho = \frac{m}{V}$), which for an ideal gas under specified pressure and temperature is formulated as $\rho = \frac{PM}{RT}$.

Specific Gravity

The dimensionless ratio of the density of a substance to the density of pure water at $4^\circ\text{C}$ ($\rho_{\text{H}_2\text{O}} \approx 1\,\text{g/mL}$).

Vapor Density (V.D.)

The relative density of a gas compared to hydrogen gas ($\text{H}_2$) at the same temperature and pressure, satisfying the relationship $M_{\text{gas}} = 2 \times \text{V.D.}$

Percentage by Mass (Mass %)

The mass of a specific component in a sample divided by the total mass of the sample, multiplied by $100\%$.

Percentage by Mole (Mole %)

The number of moles of a specific component divided by the total number of moles of all components in a mixture, multiplied by $100\%$.