Water of Crystallisation Some crystalline compounds incorporate a fixed number of water molecules into their structural lattice. This water is referred to as the water of crystallisation. Key Definitions A hydrated compound is a substance that contains water of crystallisation within its structure. A well-known example is hydrated copper(II) sulfate, CuSO₄·5H₂O, which is blue. An … Read more
Defining Atomic Mass To compare the masses of different atoms, chemists use a standard scale. All atomic masses are measured relative to a standard atom, which is an isotope of carbon, carbon-12. Unified Atomic Mass Unit (u) The unified atomic mass unit is the standard unit for atomic masses. It is defined as exactly one-twelfth … Read more
Defining Isotopes Isotopes are atoms of the same element that possess the same number of protons but a different number of neutrons. This means they share the same atomic (proton) number (Z) but have different mass (nucleon) numbers (A). Because isotopes of an element have the same number of protons, they also have the same … Read more
An atom, once believed to be the smallest indivisible unit of matter, is fundamentally composed of three key types of subatomic particles: the proton, the neutron, and the electron. The arrangement and number of these particles within an atom determine the chemical identity and properties of an element. The vast majority of an atom’s volume … Read more
Inside the Atom The modern understanding of atomic structure is centered on a model where the atom is mostly empty space. At the center lies a very small, dense nucleus, which contains positively charged protons and neutral neutrons. Collectively, protons and neutrons are known as nucleons. The nucleus contains nearly all the mass of the … Read more
Ionization energy is a fundamental concept that provides strong evidence for the arrangement of electrons in shells and sub-shells within an atom. It measures the energy required to remove electrons from gaseous atoms or ions. First Ionization Energy The first ionization energy (IE₁) is defined as the energy required to remove one electron from each … Read more
Quantum Subshells The principal quantum shells (energy levels) in an atom, except for the very first one, are split into subshells. These are identified by the letters s, p, and d. Each principal quantum shell contains a specific number of subshells, and within any given shell, the energy of the electrons increases in the order … Read more
Atomic Radius The atomic radius of an element is a measure of the size of its atoms, typically the distance from the nucleus to the outermost electron shell. For elements that exist as diatomic molecules, this is often measured as half the distance between the nuclei of two covalently bonded atoms (the single covalent radius). … Read more