THE LANGUAGE OF CHEMISTRY

Vocabulary flashcards covering chemical definitions, elements, compounds, valency, radicals, and formulas from the lecture notes.

Chemistry

A branch of science in which we study about matter, its nature, structure, and the changes it undergoes when subjected to different conditions.

Molecule

The smallest particle of matter which is capable of independent existence.

Pure substance

A substance made up of molecules containing the same kind of atoms, exhibiting a definite composition and uniform properties throughout.

Element

A simple and pure form of matter which cannot be decomposed into simpler substances.

Atom

The smallest particle of an element which may or may not exist independently but can take part in a chemical reaction.

Atomicity

The number of atoms present in a molecule of an element.

Monoatomic molecules

Molecules consisting of only one atom, such as noble gases ($Helium$, $Neon$, $Argon$), metals, and carbon.

Diatomic molecules

Molecules containing two atoms, such as $Hydrogen$ ($H_2$), $Oxygen$ ($O_2$), and $Nitrogen$ ($N_2$).

Compound

A substance formed by the chemical combination of two or more elements in a fixed proportion.

Mixture

An impure substance formed by mixing two or more pure substances in any proportion such that they do retain their individual properties and do not undergo a chemical change.

Jons Jakob Berzelius

The Swedish chemist who suggested using the initial letter of an element's name in capitals as its symbol.

IUPAC

International Union of Pure and Applied Chemistry; the body that approves and guides the universal system of chemical symbols and formulae.

Symbol

The short form that stands for the atom of a specific element or the abbreviation used for the name of an element.

Wolfram

The German name for Tungsten, which provides its chemical symbol $W$.

Valency

A measure of an element's combining power; modernly defined as the number of electrons an atom can lose, gain, or share during a chemical reaction.

Ion

A positively or negatively charged atom (or group of atoms) formed by the loss or gain of electron(s).

Valence electrons

The electrons present in the outermost shell (valence shell) of an atom.

Cations

Positively charged ions formed when atoms lose electrons.

Anions

Negatively charged ions formed when atoms gain electrons.

Variable valency

The ability of certain elements to exhibit more than one valency due to the loss of electrons from both the valence shell and the penultimate shell.

Stock notation

A method in chemical nomenclature using Roman numerals in brackets to represent the valency of a basic radical.

Molecular formula

A symbolic representation of a molecule of an element or a compound using symbols and numerical subscripts.

Radical

An atom or a group of atoms of the same or different elements that behaves as a single unit with a positive or negative charge.

Basic radicals

Positively charged radicals (cations) formed when a base loses its hydroxide ion ($OH^-$).

Acidic radicals

Negatively charged radicals (anions) formed by the removal of hydrogen ion ($H^+$) from acids.

Free Radicals

Atoms, molecules, or ions containing at least one unpaired valence electron, making them highly unstable and reactive.

Hydroxyl radical ($OH^{\bullet}$)

Known as the detergent of the atmosphere, it plays a vital role in removing air pollutants like methane and carbon monoxide.

Oxidative stress

A condition in the human body caused by an excess of free radicals, which can damage cell membranes, proteins, and DNA.

Antioxidants

Substances like $Vitamin\,C$ and $Vitamin\,E$ that help neutralize excess free radicals in the body.

Chemical equation

The symbolic representation of a chemical reaction using the symbols and formulae of the substances involved.

Skeletal equation

A chemical equation that represents a chemical change but is unbalanced, meaning the number of atoms for each element is not equal on both sides.

Balanced equation

An equation where the total number of atoms of each element in the reactants is equal to the number of atoms in the products.

Law of Conservation of Matter

A law stating that matter is neither created nor destroyed during a chemical reaction.

Relative Atomic Mass (RAM)

The number of times one atom of an element is heavier than $\frac{1}{12}$ of the mass of an atom of $carbon-12$.

Atomic mass unit (amu)

Defined as $\frac{1}{12}$ the mass of a $carbon-12$ atom, equal to approximately $1.6605 \times 10^{-24}\,g$.

Relative Molecular Mass (RMM)

The sum of the relative atomic masses of all atoms present in one molecule of a substance.

Percentage composition

The percentage by weight of each element present in a compound.

Empirical formula

The formula which gives the simplest whole number ratio of atoms of different elements present in one molecule of a compound.