Developing Metals - Transition Metals

Question 1

which two elements in the first row of the d-block are outliers in terms of electron configuration?

Answer 1

chromium

copper

Question 2

what is the electron configuration of chromium?

Answer 2

[Ar]3d⁵4s¹

Question 3

what is the electron configuration of copper?

Answer 3

[Ar]3d¹⁰4s¹

Question 4

why do chromium and copper have different electron configurations?

Answer 4

they are more stable with full 3d orbitals:

chromium has 1 unpaired in each d-orbital which is more stable than 1 being empty so one is taken from s orbital

copper has full paired electrons in each d-orbital

Question 5

what are transition metals?

Answer 5

the metals in groups 4-11

Question 6

why aren’t groups 3 and 12 transition metals?

Answer 6

when group 3 are ionised, they act like group 2

when group 12 are ionised - they have an empty d-orbital so do not act like transition metals

Question 7

what are the properties of transition metals?

Answer 7

form coloured compounds

variable oxidation states

good catalysts

complex formations

Question 8

why do transition metals exist in a number of oxidation states?

Answer 8

there are several stable arrangements of the d-electrons and s-electrons

Question 9

why is Fe³⁺ more stable than Fe²⁺?

Answer 9

Fe²⁺ d-electrons = [II][I][I][I][I]

Fe³⁺ d-electrons = [I][I][I][I][I]

as none of the d-electrons in Fe³⁺ are paired - more stable because easy to drop the extra electron in Fe²⁺

Question 10

what colour is Fe²⁺ in solution?

Answer 10

brown/orange

Question 11

what colour is Fe³⁺ in solution?

Answer 11

green

Question 12

in oxidation of transition metals, which electrons are always lost first?

Answer 12

s-orbital electrons

Question 13

what colour is V²⁺ in solution?

Answer 13

lilac

Question 14

what colour is V³⁺ in solution?

Answer 14

green

Question 15

what colour is V⁴⁺ in solution?

Answer 15

blue

Question 16

what is the colour of V⁵⁺ in solution?

Answer 16

yellow

Question 17

what are REDOX titrations used for?

Answer 17

determining the amount of a transition metal in a substance

Question 18

why aren’t indicators needed in redox titrations?

Answer 18

transition metals are coloured in solution - act as indicators themselves

Question 19

describe the steps of a redox titration using MnO₄^- and C₂O₄^2-

Answer 19

1. put standard solution of MnO₄^- in the burette
2. use a graduated pipette to transfer C₂O₄^2- in a conical flask
3. add an acid catalyst (not HCl)
4. heat flask to 60ºC
5. titrate until pink-purple precipitate persists due to excess MnO₄^-
6. repeat to get concordant results

Question 20

why do transition metals make good catalysts?

Answer 20

ability to change oxidation state easily

available 3d and 4s electrons

Question 21

why are transition metals good homogenous catalysts?

Answer 21

easy to switch between oxidation states as an aqueous ion

Question 22

why are transition metals good heterogenous catalysts?

Answer 22

use 3d and 4s electrons to form weak chemisorption with reactants

once reaction occured on surface, bonds easily break to release products

Question 23

what is chemisorption?

Answer 23

type of adsorption where the reactants form a chemical bond with the catalyst surface