Definitions

Question 1

isotope

Answer 1

atoms of the same element with the same number of protons and electrons but a different number of neutrons

Question 2

relative atomic mass

Answer 2

the average mass of an element compared to 1/12 of the mass of a carbon 12 atom

Question 3

dative covalent bond

Answer 3

a covalent bond in which the shared pair of electrons originates from the same atom

Question 4

first ionisation energy

Answer 4

the energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of positive ions

Question 5

orbital

Answer 5

a region in soace where it is likely to find an electron, each orbital can hold up to two electrons with opposite spins

Question 6

second ionisation energy

Answer 6

the energy required to remove one mole of electrons from one mole of gaseous positive ions to form one mole of gaseous dipositive ions

Question 7

the octet rule

Answer 7

atoms on main group elements combine so they each have 8 electrons

Question 8

covalent bond

Answer 8

the electrostatic attraction between two nuclei and a shared pair of electrons between theme

Question 9

enthalpy of formation

Answer 9

the enthalpy change when one mole of a compound in its standard state is formed from its elements in their standard states under standard conditions

Question 10

enthalpy of combustion

Answer 10

the enthalpy change when one mole of an element or compound is completely burnt in excess oxygen under standard conditions

Question 11

hess law

Answer 11

the enthalpy change for a reaction is independent of the route taken to achieve it

Question 12

mean bond enthalpy

Answer 12

the enthalpy change when one mole of a particular type of bond is broken or made average over different molcules

Question 13

bond enthalpy

Answer 13

the enthalpy change to break one mole of covalent bonds in the gase phase