Definitions Flashcards
Atomic number (z)
the number of protons in the nucleus of an atom
Mass number (a)
the total number or protons and neutrons in the nucleus of an atom
Relative isotopic mass (RIM)
the mass of an atom of a particular isotope of an element, relative to 1/12th the mass of a carbon-12 atom
Relative atomic mass (RAM, Ar)
the average mass of an atom of an element, relative to 1/12th the mass of a carbon-12 atom
Orbital
a region of 3D in which there is a probability of finding an electron
1st ionisation energy
energy required to remove one electron from each atom, in a mole of gaseous atoms
2nd ionisation energy
energy required to remove one electron from each 1+ ion, in a mole of gaseous 1+ ions
Periodicity
trends in the properties of elements repeat in successive periods of the periodic table
Electronegativity
the ability of an atom of an element to attract a pair of bonding electrons
Oxidised
loss of electrons and increase in oxidation number
Reduced
gain of electrons and decrease in oxidation number
Oxidising agent
causes oxidation by taking away electrons
Reducing agent
causes reduction by giving electrons
Hess’s law
ΔH for a reaction is independent of the route taken
Standard enthalpy of formation
enthalpy change when one mole of a substance is formed from its elements in their standard states at 298K and 100kPa
Standard enthalpy of combustion
enthalpy change when one mole of a substance is completely oxidised in excess oxygen at standard conditions 298K and 100kPa
Why do we do Hess cycles
when it requires heat energy and we cant measure temp change
Mole
the amount of any substance which occupies a volume of 24dm3 at room temp and pressure
Avogadros number
the number of things in a mole
Ionic bonding
the electrostatic attraction between oppositely charged ions in all directions
Anions
negative ions
Cations
positive ions
Covalent bonding
the electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Dative bond
is a covalent bond where only one of the bonded atoms donated both electrons being shared
Symmetrical molecule
all the atoms around the central atom are the same and there are no lone pairs on the central atom
Unsymmetrical molecule
the central atom has two or more different atoms or the central atoms has one or more lone pairs
Disproportionation
A reaction where one element in one species is both oxidised and reduced
Lattice energy (LE)
Energy released when one mole of an ionic compound is formed from gaseous ions
Standard enthalpy of hydration
Enthalpy change when one mole of gaseous ions are hydrated by excess water
Standard enthalpy of solution
Enthalpy change when on mole of ionic solid dissolves in excess water
What is entropy
A measure of the amount of disorder
Rate or reaction
Change in quantity of reactant or product over time
Activation energy
The minimum energy required for a collision to be successful
Homogenous catalyst
Catalyst is in the same state/phase as the reactants
Heterogenous catalyst
The catalyst is in a different phase from reactants
Adsorption
A process in which atoms, molecules or ions are held on the surface of the solid
Desorption
Removal of an adsorbed molecule, atom or ion from an adsorbent
Half life
Time taken for the concentration of reaction to halve
Chiral molecule
A molecule containing a carbon atom which has four different groups bonded to it
Stability constant Kstab
The equilibrium constant for the formation of a complex ion in a solvent from its constituent ions
Large Kstab
stable complex
Small Kstab
unstable complex
Standard electrode potential
- The emf of a half cell measured relative to the standard hydrogen electrode
- All solutions at 1moldm-3 concentration and gases at 100kPa
- At 298 K
Lattice enthalpy of formation
Enthalpy change when:
- 1 mole of a solid ionic compound is formed
- from its gaseous ions
- under standard conditions
Enthalpy change of atomisation
Enthalpy change when:
- 1 mole of gaseous atoms is made
- from an element
- in its standard state
Enthalpy change of solution
Enthalpy change when:
- 1 mole of an ionic substance is dissolved in the minimum amount of solvent
- to ensure no further enthalpy change is observed upon further dilution
