A level Chemistry Flashcards
Element
A substance which cannot be broken down by any chemical process. All the atoms within it have the same atomic number (a material with only one type of atom).
Ion
An electrically charged particle formed from an atom or group of atoms which have lost or gained electrons.
Mass Number
The number of protons + the number of neutrons in the nucleus.
Atomic Number
The number of protons in an atom
Isotopes
Atoms which have the same number of protons but different numbers of neutrons. They have the same atomic number but different neutron numbers.
Relative Isotopic Mass
The mass of an atom of a particular isotope of an element relative to 1/12 of the mass of carbon–12 atom, defined as 12 exactly.
Relative Atomic Mass
The weighted average mass of atoms of an element in their natural relative isotopic abundance compared to the carbon 12 isotope taking the mass of 12 C =
12.0000.
Ionic Bond
An electrostatic attraction between oppositely charged positive cations and negative anions. It is usually formed by electron transfer from a metal atom to a non metal.
Covalent Bond
A shared pair of electrons one from each donor atom
Covalent Bonding
The electrostatic attraction between the nuclei and the bonding pair of electrons which holds the 2 nuclei together.
Bond Length
The distance between the nuclei of the two atoms that are covalently bonded together.
Double Covalent Bond
A covalent bond in which two pairs of electrons are shared between two atoms.
Dative Covalent Bond
Is a shared pair of electrons both from one donor atom
Allotropes
Two or more forms of the same element in which the atoms or molecules are arranged in different ways
Metallic Bonding
The electrostatic attractions between positive metal
cations and the delocalised electrons.
Valence Shell Electron Pair Repulsion (VSEPR) Theory
- Bonding pairs of electrons around a central atom repel each other and arrange themselves as far apart around the central atom to minimise repulsion
- lone pairs of electrons are held more closely to the central atom and so exert a greater repelling effect than bonding pairs. This reduces the bond angle by approx 2 o per lone pair.
Bond Angle
The angle between two covalent bonds in a molecule or giant covalent structure
Bond Length
The distance between the nuclei of two atoms linked by one or more covalent bonds.
Polar Covalent Bond
A covalent bond where the bonding pair of electrons are not shared equally by the two atoms in the bond.The shared electrons are attracted towards the atom with the stronger pull from the nucleus which is described as more electronegative The bonds have a slightly positive pole + at one end and a negative one - at the other.
Electronegativity
A measure of its ability to attract the shared pair of
electrons in a covalent bond. It is a comparative scale based on Fluorine = 4.0
Hydrogen Bond
A particularly strong permanent dipole-permanent dipole attraction between the lone pair of electrons on a very electronegative atom (N, O or F) and a hydrogen atom directly covalently bonded to another very electronegative N, O or F atom.
Atom
The smallest uncharged particle of an element.
Compound
Made up of two or more elements chemically joined together
Mole
The amount of substance containing the Avogadro number of atoms, molecules or groups of ions. Where Avogadro’s number is 6.023 * 10^23 mol -1. Or The amount of substance containing as many particles as there are carbon atoms in 12g of 12 C
Empirical Formula
The simplest whole number ratio of the atoms of each element in the substance. It is also the simplest whole number ratio of moles of atoms in a substance.
Molecular Formula
Shows the number of atoms of each element in
the compound.
Parts per Million
The mass of solute per million grams of solvent.
Relative Formula Mass
The weighted mean mass of a formula unit compared to the carbon-12 isotope taking 12 C = 12.0000.
Molar Mass
The mass of one mole of any substance in g/mol.