Are you a chemistry student? Visit A-Level Chemistry to download comprehensive revision materials - for UK or international students!

Atomic Structure

Definition According to Dalton’s theory atom is smallest particle which could not be divided any further. Atom is the entity that take part in a chemical reaction. For example, He and Ne, etc. have atoms, which exists independently. While atoms of hydrogen, nitrogen and oxygen do not exist independently. An atom is further composed of … Read more

Double Covalent Bond

History Initially, the term covalence concerning bonding was used in 1919, by Irving Langmuir in an American journal known as the Journal of the American Chemical Society under the title of “The Arrangement of Electrons in Atoms and Molecules.” Langmuir wrote in his journal that “we shall denote by the term covalence the number of … Read more

First Ionization Energy

Definition The ionization energy of an element is the minimum energy required to remove an electron from the valence shell of an isolated gaseous atom to form an ion [1]. For example:         Mg → Mg + e–             ΔH = 738kjmol-1 Explanation In the gaseous phase, the atoms and ions are isolated and are free from … Read more

Van der Waals Force

Introduction The van der Waals force was named after a Dutch scientist Johannes Diderik van der Waals (1837-1923). This is considered as the first type of intermolecular forces between atom and molecules. Like ionic or covalent bonds, these attraction forces do not result from a chemical bond as they are comparatively weak and hence can … Read more

Ionic Bond

Introduction of Ionic Bond Ionic bond is a kind of chemical bond which involves an electrostatic attraction between two oppositely charged ions because of the complete transfer of valence electrons between them. As for example: metals such as sodium losses electrons to to become positive ion, whereas non-metal such as chlorine accepts electrons to become … Read more

Atomic Orbitals

Atomic Orbitals Definition Orbit is the definite path of an electron that moves around the nucleus in an atom. This is similar to a planet, moves around the sun. Orbitals are the space or region around the nucleus where the electron are calculated to be present. So orbits and orbitals have totally different meanings. Shapes … Read more

Metallic Bond

Metallic Bond Definition Metallic bonding is a special type of bonding that holds the metals together in metal crystal. This bond is neither covalent nor ionic. Metals have tendency to give up electrons and none is their to accept it. There are several theories to explain this type of bonding, among them the electron sea … Read more

Atomic radius

Definition of atomic radius The atomic radius is the size of the atom, typically measured by the distance from the nucleus of the atom to the electron clouds around the nucleus. As there are no physical existence of orbital in atoms, it is difficult to measure the atomic radius. Thus sometime different methods are used … Read more