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Neutron
A subatomic particle found in the nucleus of an atom, with no charge.
Ion
A charged particle formed when an atom loses or gains electrons.
Proton
A subatomic particle found in the nucleus of an atom, with a positive charge.
Electron
A subatomic particle with a negative charge that orbits the nucleus of an atom.
Atomic Number
The number of protons in the nucleus of an atom, denoted by Z.
Mass Number
The total number of protons and neutrons in the nucleus of an atom, denoted by A.
Isotope
Atoms of the same element with the same number of protons but different numbers of neutrons.
Relative Atomic Mass
The average mass of an element considering the abundance of its isotopes, denoted by Ar.
Relative Formula Mass
The sum of the relative atomic masses of all atoms in a chemical formula, denoted by Mr.
Energy Shells
The regions around the nucleus of an atom where electrons are arranged in different levels or energy states.
Subshells
Subdivisions of energy levels within an atom, denoted by the letters s, p, d, f, etc., each with a specific maximum number of electrons it can hold.
Electron Configuration
The distribution of electrons in the energy levels and subshells of an atom, represented by numbers and letters indicating the energy level, subshell type, and number of electrons in that subshell.
Electron Arrangement
The specific organization of electrons in the energy levels and subshells of an atom, often depicted using diagrams or simple notation to show the number of electrons in each level or subshell.
Periodic Table
A tabular arrangement of the chemical elements, organized by atomic number, electron configuration, and recurring chemical properties.
S-block
The section of the periodic table consisting of groups 1 and 2, where elements have their outermost electrons in an s subshell.
P-block
The section of the periodic table consisting of groups 3 to 0, where elements have their outermost electrons in a p subshell.
Atomic Number
The number of protons in the nucleus of an atom, determining the element's identity in the periodic table.
Group
Vertical columns in the periodic table where elements share similar chemical properties due to having the same number of electrons in their outer shell.
Period
Horizontal rows in the periodic table where properties of elements change gradually across the row.
Electron Configuration
The distribution of electrons of an atom or molecule in atomic or molecular orbitals.
Full Outer Shell
A stable electron configuration achieved by some elements when they gain or lose electrons to have a complete outer shell.
Ionisation Energy
The energy required to remove an electron from an atom or ion in the gaseous state.
Sodium Ion
An ion of sodium with a 1+ charge formed by losing one electron.
Three Factors Affecting Ionisation Energy
Nuclear charge, distance from the nucleus, and shielding by inner electrons affect the ease of removing an electron.
Periodic Table Trends in Ionisation Energies
Ionisation energy decreases down a group and generally increases across a period due to changes in nuclear charge, distance from the nucleus, and shielding.
Simple Ions
Elements in the s-block and p-block form ions with full outer electron shells, leading to predictable charges based on group number.
Transition Metals
Metals between Groups 2 and 3 that form ions with varying charges, known as oxidation numbers, unlike s-block metals.
Oxidation Number
The oxidation number of an atom tells you how many electrons the atom has donated or accepted when it has reacted, also known as the charge on an atom.
Roman Numerals
Roman numerals are used to show the oxidation number of certain elements, where (I) = +1, (II) = +2, (III) = +3, and so on.
Intermolecular Bonds
Weak forces of attraction that form between molecules, distinct from the strong bonds within a molecule.
Electronegativity
The ability of an atom to attract electrons in a covalent bond, with fluorine being the most electronegative element.
Ionic Bonding
The type of bond that forms when electrons are transferred from one atom to another, resulting in the attraction between oppositely charged ions.
Covalent Bonding
The bond that forms when atoms share pairs of electrons to achieve a full outer shell, resulting in the formation of a molecule.
Ions
Charged particles that form when atoms lose or gain electrons.
Electron Transfer
The process where electrons are moved from one atom to another to form ions.
Dot-and-Cross Diagram
A diagram that represents the transfer of electrons between atoms using dots for electrons from one atom and crosses for electrons from another.
Ionic Compound
A compound formed by the attraction between positively and negatively charged ions.
Ionic Formula
The representation of an ionic compound showing the ratio of positive to negative ions.
Melting Point
The temperature at which a solid substance changes into a liquid.
Electrical Conductivity
The ability of a substance to conduct electricity.
Solubility
The ability of a substance to dissolve in a solvent, usually water.
Giant Ionic Structures
Large, closely packed regular arrays of ions formed by ionic compounds.
Covalent Molecule
A molecule formed by atoms sharing electrons in covalent bonds.
Multiple Covalent Bond
A bond formed when two atoms share more than one pair of electrons.
Dative Covalent Bond
A covalent bond where both shared electrons come from the same atom.
Hydrogen Fluoride (HF)
A small covalent molecule where hydrogen is bonded to fluorine. It has a dot-and-cross diagram showing the bonding electrons and lone pairs of electrons.
Nitrogen Gas
Despite nitrogen atoms being strongly bonded to each other in each molecule, nitrogen is a gas at room temperature due to the weak intermolecular bonds between the molecules.
Lone Pairs
Electron pairs in a molecule that are not shared between atoms, affecting the physical properties of covalent molecules.
Hydrogen Bonds
The strongest type of intermolecular bond formed between covalent molecules with lone pairs on nitrogen, fluorine, or oxygen atoms bonded to hydrogen(s), leading to high boiling and melting points and increased solubility.
Period 3 oxides
Compounds formed by elements in Period 3 of the periodic table, showing a transition in bonding types from ionic to covalent across the period.
Ionic bonding
A type of chemical bonding that involves the transfer of electrons from one atom to another, resulting in the formation of ions held together by electrostatic forces.
Covalent bonding
A type of chemical bonding where atoms share pairs of electrons to achieve a stable electron configuration, forming molecules.
Melting point
The temperature at which a solid substance changes into a liquid state at standard pressure.
Chemical equation
A symbolic representation of a chemical reaction showing the reactants on the left side and the products on the right side.
Balancing equations
The process of ensuring that the number of atoms of each element is the same on both sides of a chemical equation by adjusting coefficients.
State symbols
Symbols used in chemical equations to indicate the physical state of a substance (solid, liquid, gas, or aqueous).
Symbol equation
A type of chemical equation that includes the chemical formulae of the reactants and products, showing the atoms involved in the reaction.
Ionic equation
A type of chemical equation that represents the species that are actually involved in a reaction in solution, focusing on ions.
Charge balance
Ensuring that the total charge on the reactant side of an ionic equation is equal to the total charge on the product side.
Metallic Bonds
Bonds that hold metals together in a lattice structure, formed by the attraction between positive ions and free electrons.
Electron Shielding
The phenomenon where inner electrons shield outer electrons from the attraction of the positive nucleus, leading to weaker metallic bonds.
Group 2 Metals
Metals in Group 2 of the periodic table that lose two electrons during reactions, becoming more reactive as you go down the group.
Reactivity
The tendency of an element to undergo chemical reactions, increasing as you go down Group 2 due to easier donation of outer electrons.
Ionization Energy
The energy required to remove an electron from an atom, affected by factors like nuclear charge, electron shielding, and distance from the nucleus.
Potassium hydroxide
KOH
Sodium hydroxide
NaOH
Acids
Substances with a pH less than 7.
Bases
Substances with a pH greater than 7.
pH Scale
Measures how acidic or basic a substance is, ranging from 0 to 14.
Neutralization reaction
Reaction between an acid and a base to form a salt and water.
Proton donors
Acids release hydrogen ions (H+) when mixed with water.
Proton acceptors
Bases accept hydrogen ions (H+).
Skeletal formula
Representation of a molecule showing the carbon skeleton and functional groups.
Displayed formula
Shows all atoms and bonds in a molecule.
Molecular formula
Indicates the number of atoms of each element in a molecule.
Homologous series
Groups of organic compounds with similar properties and functional groups.
Alkanes
Hydrocarbons with only single bonds between carbon atoms.
Saturated molecules
Molecules like alkanes where all available bonds are formed.
Complete combustion
Reaction of a fuel with oxygen to produce carbon dioxide and water.
Methane
CH4
Alkenes
Hydrocarbons containing a carbon-carbon double covalent bond (C=C) somewhere in the carbon chain, making them unsaturated molecules.
Isomers
Molecules with the same molecular formula but different structures.
Polymers
Long, chain-like molecules built up from lots of repeating units (monomers), formed by linking together small alkenes under the right conditions.
Hydrogen Bonds
Strong intermolecular bonds formed between the slightly positive hydrogen atom in the -OH group of alcohols and lone pairs of electrons on oxygen atoms in other alcohol molecules.
Disproportionation
A rare type of chemical reaction where an element in a reactant is both oxidized and reduced simultaneously.
Displacement
A reaction where one element displaces another, less reactive element from a compound.
Dehydration
The removal of water from a compound by heating, often resulting in the formation of a C=C bond in organic molecules.
Cracking
The thermal decomposition of long-chain hydrocarbon molecules into shorter-chain alkanes and alkenes, requiring high temperatures, pressures, and a catalyst.
Condensation
A reaction where atoms are added to an unsaturated bond to make it saturated, often forming a simple molecule like water.
Combustion
The chemical reaction between a fuel and oxygen, producing carbon dioxide and water in complete combustion.
Precipitation
The formation of a solid (precipitate) in a solution due to a chemical reaction or change in temperature affecting solubility.
Oxidation
The loss of electrons or gain of oxygen in a chemical reaction, opposite of reduction.
Hydrogenation
The addition of hydrogen across a C=C bond, resulting in the saturation of the bond.
Neutralisation
The reaction between a basic compound and an acid, producing a salt, water, and other products.
Exothermic
Any chemical reaction that releases heat energy, with products having less energy than the reactants.
Elimination
The removal of a small molecule from a larger molecule, often involving the removal of H2O or H2.
Electrolysis
A process using electricity to break down a compound, requiring the reactants to be in a liquid state.
Endothermic
Any chemical reaction that absorbs heat energy, with products having more energy than the reactants.
Substitution
A reaction where an atom or group of atoms in a molecule is replaced by a different atom or group of atoms.
Reduction
The gain of electrons or loss of oxygen in a chemical reaction, always occurring together with oxidation.