chapter 7

Question 1

what did antoine lavoisier do?

Answer 1

made a list of substances he thought were elements

Question 2

what did johann dobereiner do?

Answer 2

took 3 elements with similar properties (triads)
atomic mass of middle elements were roughly halfway between the other two

Question 3

what did john newlands do?

Answer 3

suggested putting elements in order of atomic mass
every 8th element was similar
only worked for first 15

Question 4

what did dimitri mendeleev do?

Answer 4

arranged elements in increasing atomic mass
left gaps for elements not discovered yet
put elements with similar properties in vertical groups
he swapped elements around to fit group properties

Question 5

what are the group trends in the periodic table?

Answer 5

elements in same group have same number of electrons in outer shell and same number of electrons in each subshell

Question 6

what is first ionisation energy?

Answer 6

the energy needed to remove 1 electron from each atom of an element in 1 mole of gaseous atoms

Question 7

what is the first ionisation energy equation?

Answer 7

X(g) –> X+(g) + e-

Question 8

what factors affect ionisation energy?

Answer 8

atomic radius
nuclear charge
inner shell shielding

Question 9

how does atomic radius affect ionisation energy?

Answer 9

greater distance between nucleus and outer shell electrons the weaker the nuclear attraction between nucleus and outer electrons

Question 10

how does nuclear charge affect ionisation energy?

Answer 10

more protons in the nucleus means greater nuclear attraction between nucleus and outer shell electrons

Question 11

how does inner shell shielding affect ionisation energy?

Answer 11

inner shell electrons repel outer shell electrons
repulsion (shielding effect) reduces attraction between nucleus and outer electrons

Question 12

what is the trend down a group for ionisation energies?

Answer 12

first ionisation energies decrease down a group as atomic radius increases

Question 13

what element group has the highest ionisation energies?

Answer 13

noble gases

Question 14

what is the general trend for ionisation energies across a period?

Answer 14

first ionisation energies increase across a period as nuclear charge increases

Question 15

what are the reasons for falls in ionisation energies?

Answer 15

linked to existence of sub-shells, their energies and how orbitals fill with electrons

Question 16

why are there falls in ionisation energies?

Answer 16

e.g. easier to remove an electron from a 2p subshell than 2s subshell

Question 17

why is there a fall of first IE between nitrogen and oxygen?

Answer 17

easier to remove a spin-paired 2p electron oxygen as paired electrons repel each other

Question 18

how many ionisation energies does an element have?

Answer 18

as many IEs as electrons

Question 19

what does the equation for a second ionisation energy look like?

Answer 19

He+(g) –> He2+(g) + e-

Question 20

why is the second ionisation energy of helium greater than the first?

Answer 20

nuclear attraction on remaining electrons increases as more protons left than electrons (one electron has been removed)

Question 21

what does a large difference in ionisation show?

Answer 21

changes to another shell which is closer to the nucleus