TRANSITION ELEMENTS

Question 1

Transition elements

Answer 1

a transition element is a d block element that can form atleast a stable ion with a partially filled d sub shell.

Question 2

exception

Answer 2

scandium and zinc are not transition elements.
- copper and chromium for an exception of the orbital sequence

Question 3

why is scandium and zinc not a transition element

Answer 3

• scandium only has one ion which is sc3+ and since it has an empty d subshell its non a transition element.
• zinc only has one ion zn2+ and since it has a full d subshell its not a transition element as well.

Question 4

why are copper and chromium an exception

Answer 4

because an electron from 4s orbital moves into 3d to create a more stable full or half full 3d sub shell.

Question 5

properties of transition elements

Answer 5

1. variable oxidation states.
2. complex ions
3. good catalysts.

Question 6

variable oxidation states

Answer 6

• because electrons sit very closelt in 3d and 4s energy. so same amount of energy is used for loss and gain of electrons.

Question 7

coloured ions

Answer 7

vanadium
V2+ – VIOLET
V3+ – GREEN
VO2+ ( 2 AS A POWER) - BLUE
V0 + – YELLOW
2

Question 8

Complex ion

Answer 8

a complex ion is where a central transition metal ion is surrounded by ligands bonded by a dative covalent or a co ordinate bond.

Question 9

ligands

Answer 9

ligands are atoms, ion or molecules that have atleast one lone pair of electrons. they are monodentate, bidentate or polydentate.

Question 10

monodentate ligands

Answer 10

ligands which have only one lone pair of electrons. example : water, ammonia or chlorine molecule.

Question 11

bidentate and polydentate

Answer 11

• etahne dioate, ehane- 1,2 diamine
  EDTA+

Question 12

Complex shapes

Answer 12

• tetrahedral, linear, octahedral or square planar

Question 13

co ordination number of 6 forms

Answer 13

octahedral(90)

Question 14

co ordination number of 4 forms

Answer 14

tetrahedral (109.5) or square planar(90)

Question 15

co ordination number of 2 forms

Answer 15

linear, 180, example is tollens reagent

Question 16

formula to find total oxidation state of metal

Answer 16

total o.s of metal = total o.s or overall charge - total o.s of ligands.

Question 17

haemoglobin

Answer 17

haemoglobin is a protein containing the component haem which is a multi dentate ligand
- haemoglobin is in octahedral shape with an iron metal ion bonded by 4 nitrogen ligands, plus one nitrogen ligand bonded to globin protein and one oxygen or water ligand also bonded to the central iron ion.

Question 18

oxygen and water bonded to haemoglobin

Answer 18

• oxygen replaces water in a area of higher oxygen concentration and binds to form oxy haemoglobin which is transported around the body.
• oxyhaemoglobin delivers oxygen in place of need and is replaced by water molecule and oxyhaemoglobin returns back to the lungs to start the process all over again.

Question 19

carbon monoxide and haemoglobin

Answer 19

• carbon monoxide also known as the silent killer, the co ligand replaces the water ligand and binds strongly with the central metal ion.
• binding is strong so its not readily replaced by oxygen ligands
• this results in oxygen starvation.

Question 20

chelate effect

Answer 20

bi dentate and multi dentate ligands replace the monodentate ligands from complexes which is called the chelate effect.
- the increase in stability is also called chelate effect

Question 21

d - orbital splitting

Question 22

isomerism

Answer 22

• complex ion shows isomerism.
• octahedral complexes with 3 bi dentate ligands shows optical isomerism

Question 23

cis or trans isomerism

Answer 23

• octahedral complexes with 4 ligands of same type and 2 ligands of different types shows cis or trans isomerism.
• square planar complexes also shows cis or trans isomerism.

Question 24

electrons in d orbital splitting

Answer 24

when ligands attatch , orbitals gain energy and an energy gap is created.
- when light is emitted, electrons always absorb energy from the ground state to the excited state
- for the light energy to excite the electrons, the light energy must be equal to the energy gap or delta e.

Question 25

delta e depends on

Answer 25

1. central metal ion and its oxidation number
2. type of ligand
3. co ordination numbers

Question 26

energy gap formula

Answer 26

e = hv = hc/ lamda
where, e = energy gap
v = frequency of light absorbed
c = speed of light
h = plancks constant
lamda = wavelength

Question 27

coloured complexes in elements with full or empty d subshell

Answer 27

for elements with full or empty d subshell, no electrons can migrate to the higher energy level. so we see this complexes as colorless or white.

Question 28

colour depends on

Answer 28

1. type of ligand
2. shape of ligand
3. central metal ion and its oxidation state.

Question 29

colorimetry

Answer 29

• used to measure the concentration of transition metal ions in a solution.

Question 30

method of doing a colorimetry technique

Answer 30

1. the colorimeter must be set up to 0 ( calibrated) which is usually done by measuring the absorbance of a blank sample. the blank sample is the solvent used to dissolve the transiiton metal ion, usually solvent is water.
2. white light is filtered to a narrow range of frequencies which produces a mono chromatic light.
3. monochromatic light is then passed through the sample, where some light is which is held in a vessel called cuvette.
4. the light which was not absorbed passes through the detector. the detector them neasures the level of absorbance by comparing it to the absorbance in a blank sample.

Question 31

strrength of complexes

Answer 31

multidentate forms more stable complexes than monodentate ligands.
- reactions are harder to reverse.

Question 32

entropy and complexes

Answer 32

increasing entropy forms a more stable complex.