OCR a level chemistry

• An atom is the smallest unit of matter that retains the chemical properties of an element.
• Chemical bonding is the process by which atoms are held together in compounds.
• A redox reaction is a chemical reaction that involves the transfer of electrons between species.
• Energetics is the study of energy changes in chemical reactions.
• An acid is a substance that donates a proton (H+) in a chemical reaction.
• Equilibrium is a state in a chemical reaction where the rate of the forward reaction is equal to the rate of the reverse reaction.
• Periodicity refers to the repeating pattern of chemical and physical properties of elements as they are arranged in the periodic table.
• Kinetics is the study of the rates of chemical reactions and the factors that affect them.
• The Group 2 elements in the periodic table are also known as the alkaline earth metals.
• The Group 7 elements in the periodic table are known as the halogens.
• An atom consists of a nucleus, which contains protons and neutrons, and electrons that orbit the nucleus.
• The atomic number of an element is equal to the number of protons in the nucleus.
• The mass number of an atom is equal to the sum of the number of protons and neutrons in the nucleus.
• Isotopes are atoms of the same element that have different numbers of neutrons.
• The relative atomic mass of an element is the weighted average mass of all the naturally occurring isotopes of that element.
• The unit of energy used in chemistry is the joule (J).
• Endothermic reactions absorb energy from the surroundings, while exothermic reactions release energy to the surroundings.
• The enthalpy change (∆H) is the heat energy transferred in a reaction at constant pressure.
• Standard conditions for enthalpy changes are 298K (25°C) and 1 atmosphere pressure.
• The enthalpy change of a reaction can be measured using a calorimeter.
• The species that loses electrons is said to be oxidized, while the species that gains electrons is said to be reduced.
• Oxidation involves an increase in oxidation state, while reduction involves a decrease in oxidation state.
• The oxidation state of an element in its elemental form is always zero.
• The sum of the oxidation states of all the atoms in a neutral compound is zero.
• The sum of the oxidation states of all the atoms in a polyatomic ion is equal to the charge of the ion.
• There are three main types of chemical bonding: ionic bonding, covalent bonding, and metallic bonding.
• Ionic bonding occurs between a metal and a non-metal, where electrons are transferred from the metal to the non-metal.
• Covalent bonding occurs between non-metals, where electrons are shared between atoms.
• Metallic bonding occurs between metal atoms, where electrons are delocalized and shared among all the atoms.
• Ionic compounds have high melting and boiling points, and conduct electricity when dissolved in water or molten.
• A base is a substance that accepts a proton (H+) in a chemical reaction.
• The pH scale is a measure of the acidity or alkalinity of a solution, ranging from 0 to 14.
• A pH value below 7 indicates acidity, while a pH value above 7 indicates alkalinity.
• Strong acids completely dissociate in water, releasing all of their hydrogen ions.
• Weak acids only partially dissociate in water, releasing some of their hydrogen ions.
• The periodic table is organized in periods (rows) and groups (columns).
• Elements in the same group have similar chemical properties.
• The periodic table is divided into s, p, d, and f blocks based on the types of orbitals being filled.
• The s-block elements are located in groups 1 and 2, and the p-block elements are located in groups 13 to 18.
• The d-block elements are located in groups 3 to 12, and the f-block elements are located below the main body of the periodic table.