Definitions Flashcards
What is the definition of isotopes?
Atoms with the same number of protons, but a different numberof neutrons
What is the definition of the first ionisation energy?
The enthalpy change when one mole of gaseous atoms each have
an electron removed, forming one mole of gaseous ions with a single positive charge
What is the definition of relative atomic mass?
The average mass of one atom in ratio to one twelfth of the mass of
one atom of carbon-12
What is the definition of ionic bond?
The electrostatic force of attraction between oppositely charged ions formed by electron transfer
What is a Covalent bond?
A shared pair of electrons
What is the definition of a metallic bond?
The electrostatic force of attraction between the positive metal ions and the delocalised electrons
What is the definition of electronegativity?
The ability of an atom to attract electron density from a covalent bond
When do van der waals forces form?
They occur between all simple covalent molecules and the separate atoms in noble gases.
In any molecule the electrons are moving constantly and randomly. As this happens the electron
density can fluctuate and parts of the molecule become more or less negative. These instantaneous dipoles can cause dipoles to form in neighbouring
molecules. These are called induced dipoles. The induced dipole is always the opposite sign to the original one
What is the definition of standard enthalpy change of formation?
The enthalpy change when 1 mole of the compound is formed from its elements under standard conditions and standard states
What is the definition of standard enthalpy of combustion?
The enthalpy change that occurs
when one mole of a substance is combusted completely in oxygen under standard conditions and states
What is Hess’s law?
Total enthalpy change for a reaction is independent of the route by
which the chemical change takes place
What is Le Chateliers Principle?
If an external condition is changed the equilibrium will shift to oppose the change. If temperature is increased the equilibrium will shift to oppose this and move in the endothermic direction to try and reduce the temperature by absorbing heat. Increasing pressure will cause the equilibrium to shift towards the side with fewer moles of gas
to oppose the change and thereby reduce the pressure
What is oxidation?
The process of electron loss or increase in oxidation number
What is Reduction?
The process of electron gain or decrease in oxidation number
What are Reducing agents?
Electron donors
