Formal charge is a useful concept in chemistry for determining how electrons are distributed among the atoms in a Lewis structure. It helps us evaluate whether a Lewis structure is reasonable and identify the most stable resonance structure. What Is Formal Charge? Formal charge is the hypothetical charge assigned to an atom in a molecule … Read more
Dot-and-cross diagrams are a simple way to model the arrangement of outer shell electrons in atoms and ions. They are used to illustrate how electrons are involved in chemical bonding. In these diagrams, electrons from one atom are shown as dots (•) and electrons from another atom are shown as crosses (x). This helps to … Read more
Ionic Bonding Ionic bonding is the electrostatic force of attraction between positively charged ions (cations) and negatively charged ions (anions), which are arranged in a giant crystal lattice. This type of bonding typically occurs between metals and non-metals. Metal atoms lose their outer shell electrons to form stable, positively charged ions, achieving the electronic configuration … Read more
The Molar Volume of a Gas Avogadro’s hypothesis states that equal volumes of any gas, measured under the same conditions of temperature and pressure, contain an equal number of molecules. This principle allows us to relate the volume of a gas directly to the number of moles present. The molar gas volume is the volume … Read more
Defining Concentration The concentration of a solution is a measure of the amount of solute dissolved in a specific volume of solvent, which is typically water in A-Level Chemistry. The standard unit for concentration is moles per cubic decimetre (mol dm⁻³). It is important to remember the conversion between cubic centimetres (cm³) and cubic decimetres … Read more
The Principle of Balancing Equations A fundamental principle in chemistry is the law of conservation of mass, which states that atoms cannot be created or destroyed during a chemical reaction. Therefore, a chemical equation must be balanced to reflect this. A balanced chemical equation has the same number of each type of atom on both … Read more
Ionic Bonding Ionic bonding is the electrostatic force of attraction between oppositely charged ions within a giant ionic lattice structure. This type of bond typically forms between a metallic element and a non-metallic element. Formation of Ions The formation of ionic and covalent compounds is driven by the tendency of atoms to achieve a more … Read more
The formula of a compound provides essential information about the elements it contains and the ratio in which they are present. There are two main types of chemical formulae used to describe the composition of a molecule: the empirical formula and the molecular formula. Defining Chemical Formulae Understanding the distinction between an empirical and a … Read more
Stoichiometry is the study of the quantitative relationships between the amounts of reactants and products in a chemical reaction. The concept of the mole is central to all stoichiometric calculations. Relative Masses of Atoms and Molecules The Mole and Avogadro’s Constant A mole is the standard unit for the amount of a substance. One mole … Read more
Principles of Mass Spectrometry Mass spectrometry is a powerful analytical technique used to measure the mass-to-charge ratio of ions. It can determine the relative atomic mass of an element and is widely used in the identification of organic compounds. The process involves several key stages: Interpreting Mass Spectra A mass spectrum is a graph that … Read more