Atoms, Molecules and Chemical Reactions

Vocabulary practice flashcards covering fundamental laws of chemical combination, Dalton's atomic theory, chemical symbols, atomicity, valency, ions, and atomic mass standards.

Law of Conservation of Mass

A fundamental law proposed by Antoine Lavoisier stating that matter is neither created nor destroyed during a chemical reaction, which means the total mass of the products equals the total mass of the reactants.

Landolt Experiment

The experimental procedure that provided experimental verification for Antoine Lavoisier's law of conservation of mass.

Law of Constant Proportions

A law formulated by Joseph Proust stating that a given chemical substance always contains the same elements combined in a fixed proportion by mass, regardless of its source or method of preparation.

Dalton's Atomic Theory

A theory proposed by John Dalton in 'A New System of Chemical Philosophy' postulating that all matter consists of indivisible atoms that can neither be created nor destroyed, and that atoms of a given element have identical mass and chemical properties.

Parmanu

The extremely small constituent particles that make up an 'anu', as proposed by the Indian sage Kanada (Kasyapa) in his Vaishesika Sutra around $2600$ years ago.

a-tomio

The Greek word meaning 'indivisible', from which the English word 'atom' is derived.

Molecule

The smallest particle of a substance that has independent existence and retains all the chemical properties of that substance, formed by the combination of two or more atoms.

Element

A pure chemical substance whose fundamental particles contain only one type of atom.

Berzelius's System of Chemical Symbols

The naming convention suggested by John Berzelius in which the initial letter of an element's English name is written as an upper case capital letter (followed by a second lower case letter if needed) to represent the element.

Atomicity

The total number of atoms that constitute a single molecule of an element or compound.

Ozone ($O_3$)

A triatomic gas molecule composed of three oxygen atoms found in the upper atmosphere that shields the Earth from harmful ultraviolet radiation from the Sun.

Monoatomic Molecule

A molecule consisting of only a single unbonded atom, characteristic of elements such as Helium ($He$), Argon ($Ar$), Sodium ($Na$), and Copper ($Cu$).

Diatomic Molecule

A molecule made up of two combined atoms of the same or different elements, such as Hydrogen ($H_2$), Oxygen ($O_2$), Nitrogen ($N_2$), or Chlorine ($Cl_2$).

Ion

An electrically charged particle consisting of an independent atom or a group of atoms carrying a net positive or negative charge.

Cation

A positively charged ion formed by losing electrons, such as $Na^+$, $K^+$, or $Ca^{2+}$.

Anion

A negatively charged ion formed by gaining electrons, such as $Cl^-$, $O^{2-}$, or $SO_4^{2-}$.

Valency

The combining capacity number of an element that measures its power to combine with atoms of other elements and determines the atomicity of its molecules.

Variable Valency

The property shown by certain elements that exhibit more than one combining capacity, such as copper (Cuprous as $+1$, Cupric as $+2$) and iron (Ferrous as $+2$, Ferric as $+3$).

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

A standard unit of mass defined as exactly one-twelfth ($1/12\text{th}$) of the mass of a single Carbon-$12$ isotope atom, officially denoted as unified mass ($\text{u}$) under IUPAC recommendations.

Mass Spectrometer

A modern laboratory instrument used to determine the relative atomic masses of atoms with high precision.

Chemical Formula

A symbolic notation representing the composition of a compound, indicating the constituent elements and the exact number of atoms of each element present in a molecule.