Definitions

Definitions in Chemistry

Matter is anything that occupies space and has mass and made up of tiny particles.

ATOM is the smallest particle of a substance or the fundamental unit of the matter.

Atom may or may not exist independently.

An atom is composed of sub-atomic particles called proton, electrons and Neutrons.

MOLECULE: A molecule is formed when two or more atoms of same or different kind combine chemically.

ELEMENT: An element is a pure substance made up of identical atoms.

COMPOUND: Two or more atoms of different kind combine chemically in a fixed proportion to form a compound.

ATOMICITY: The number of atoms present in a molecule of an element is called its atomicity.

ATOMIC NUMBER (Z): The number of protons present in the nucleus of an atom of an element is called its Atomic number.

MASS NUMBER (A): The total number of protons and neutrons present in the nucleus of an atom of an element.

ELECTRONIC CONFIGURATION: The distribution of electrons in the shells (or) orbits in atom is

called electronic configuration.

STABLE ELECTRONIC CONFIGURATION:

                If an element has completely filled valence shell or 8 valence electrons then it is said to have stable electronic configuration.

OCTET CONFIGURATION: If an element has 8 valence electrons it is called Octet configuration.

VALENCY:

ELECTRO-VALENCY: The number of electrons that an atom of an element loses or gains to attain stability is called the electro-valency of that element.

COVALENCY: The number of electron pairs which an atom of an element shares with atoms of the same or different kind to attain stability.

ION:  An ion is an atom or a group of atoms carrying a charge (positive or negative).

Positively charged ions are termed as Cations and those which are negatively charged as Anions.

CHEMICAL BOND: The force of attraction by which two or more atoms of same or different kind are held together is a chemical bond.

ELECTROVALENT BOND: The strong electrostatic force of attraction that holds two oppositely charged ions together which are formed as a result of transfer of electron/s.

COVALENT BOND: A covalent bond is formed due to the mutual sharing of electron pairs between two non-metallic atoms.

CO-ORDINATE COVALENT BOND: It is a covalent bond in which both the electrons in the bond coming from the same atom.

ATOMIC RADIUS: The distance between the center of the nucleus and the valence shell of an atom.

ELECTRONEGATIVITY: The tendency of an element to attract the bond pair of electrons towards itself .

ELECTRON AFFINITY: The amount of energy released when an atom accepts an electron to form an anion.

IONISATION POTENTIAL: The minimum amount of energy required to remove an electron from the valence shell of an atom in gaseous state.