f block

Question 1

Which series has only one stable oxidation state?

Answer 1

Lanthanum

Question 2

Atomic size …………… from Lanthanum to Lutetium.

Answer 2

Atomic size decreases

Question 3

What is the predominant valency in the La series?

Answer 3

3+

Question 4

Pr,Nd,Tb,Dy in MO2 express what Ox.state?

Answer 4

4+

Question 5

When is Eu+ a strong reducing agent

Answer 5

When you go from +2 - +3

Question 6

Colour of Lanthanoid elements can be attributed to ….

Answer 6

• the presence of f electrons

Question 7

There is irregularity in the IE3 values. Where can it be seen?

Answer 7

Especially low values of La,Gd,Lu.

Question 8

Elements in the beginning of the series behave like …….. ; elements lower behave like ……..

Answer 8

• Ca

* Al

Question 9

Which element has a half life of 3 minutes?

Answer 9

Lawrencium

Question 10

Why can Ac elements participate more liberally in bond formation than La elements?

Answer 10

This is because the 5f orbitals are not as buried as the 4f orbital.

Question 11

Which is greater, Ac contraction or La contraction

Answer 11

Ac

Question 12

Why do the Ac elements have a great range of ox.states ?

Answer 12

This is because their 5f,6d and 7s orbitals are of comparable energies.

Question 13

Which acid reacts with all actinides?

Answer 13

Hcl

Question 14

Why are Ac elements coloured?

Answer 14

Due to:

• Charge transfer
• f-f transition

Question 15

Which compound is used in the pigment industry?

Answer 15

TiO

Question 16

What was the first synthetic element?

Answer 16

Tc