structure of an atom

Atom

The fundamental building block of matter, consisting of protons, neutrons, and electrons.

Molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Sub-atomic particles

Particles smaller than an atom, including protons, neutrons, and electrons.

Electron

A negatively charged sub-atomic particle with a negligible mass.

Proton

A positively charged sub-atomic particle found in the nucleus of an atom, with a mass of one unit.

Neutron

A sub-atomic particle with no charge, located in the nucleus of an atom, with a mass nearly equal to that of a proton.

Rutherford's model

A model proposing that an atom has a small, positively charged nucleus with electrons orbiting around it.

Thomson's model

A model suggesting that an atom consists of a positively charged sphere with negatively charged electrons embedded in it.

Bohr's model

A model proposing that electrons are distributed in discrete orbits around the nucleus without radiating energy.

Atomic number (Z)

The total number of protons in the nucleus of an atom, which defines the element.

Mass number (A)

The total number of protons and neutrons in the nucleus of an atom.

Isotope

Atoms of the same element with the same atomic number but different mass numbers.

Isobar

Atoms of different elements that have the same mass number but different atomic numbers.

Valency

The combining capacity of an element, determined by the number of electrons in its outermost shell.

Canal rays

Positively charged radiation discovered by E. Goldstein during gas discharge experiments.

Nucleus

The central core of an atom, containing protons and neutrons.

Octet rule

The tendency of atoms to gain, lose, or share electrons to achieve a full outer shell of eight electrons.

Alpha particle

A type of particle consisting of two protons and two neutrons, emitted during radioactive decay.

Electrons shells

Defined energy levels where electrons reside around the nucleus of an atom.