Class 11 Chemistry Classification of Elements and Periodicity in Properties Exam Questions

LEVEL 1

1. What would be the IUPAC name and symbol for the element of atomic no.120?

Ans: Unbinilium (Ubn)

2. State Mendeleev’s periodic law.

Ans: Physical and chemical properties of elements are the periodic function of their atomic masses.

3. How many groups are there in the p-block of periodic table?

Ans: 6

4. Explain the term electron gain enthalpy.

Ans: The enthalpy change taking place by attracting an electron towards its outermost shell of an isolated gaseous atom.

5. What are lanthanides and actinides?

Ans: (a) Lanthanides: Elements in which last electron enter in 4f sub-shell of antepenultimate shell.

       (b) Actinides: Elements in which last electron enter in 5f sub-shell of antepenultimate shell.

6.What is the general electronic configuration of d-block elements?

Ans: 

7. Arrange the following in increasing order of ionization enthalpy:- B, C, N, O.

Ans: 

8. Arrange the elements in increasing order of their size:- 

Ans: 

9. Which has the highest value of electron gain enthalpy fluorine or chlorine?

Ans: Chlorine

10. Name the first element having an incomplete 3d-level.

Ans: Na

2. Explain

a. Dobereiner triads

b. Newlands law of octaves.

Ans: Dobereiner triads: He make a group of three elements in such a way that the average of atomic masses of 1st and 3rd elements is equal to the atomic mass of the middle one such as Li, Na and K. Newlands law of Octaves: When elements were arranged in such a way that the physical and chemical properties of each eighth element were resembling.

 

 

3. Classify the elements into four blocks on the basis of electronic configuration?

Ans: On the basis of electronic configuration

a) s block elements

b) p block elements

c) d block elements

d) f block elements

 

 

4. Describe the characteristics of s-block elements?

Ans: Characteristics of s-block elements:

i) All the elements are soft metals.

ii) They have low melting and boiling points.

iii) They are highly reactive in nature.

iv) Most of them impart characteristic colours to the flame.

v) They form ionic compounds by losing their valence electrons and, thus, show oxidation states of +1 and +2 in their compounds.

vi) The elements are good reducing agents.

vii) All of them are good conductors of heat and electricity.

 

 

5. With reference to periodic table indicate,

a. Element that is in group 13 and third period both.

b. First transition element of the fourth period.

Ans: (a) Al (b) Sc

 

 

6. What do you mean by atomic radii? Discuss its variation in periodic table?

Ans: Atomic radius may be defined as the distance from the centre of the nucleus to the outermost shell containing the electrons.

The exact determination of the atomic radius of an element is not as simple as expected because:

• Along a period the atomic radii of the elements generally decreases from left to the right. It is due to increased nuclear charge from left to the right.

• The atomic radii of the elements in every group of the p[periodic table increases as we move downwards.

 

 

7. What do you mean by electro negativity? Discuss its variation in periodic table?

Ans: The electronegativity of an element is defined as the relative electron attractive tendency of its atom for a shared pair of electrons in a chemical bond.

• It depends upon the nature of the atom with which a particular atom is linked. Different scales of comparison have been given for this purpose.

• It increases along the period and decreases down the group.

 

 

8. The electronic configuration of A is 

a. To which period does it belong?

b. Write down the formula of the nitrate of A.

c. state whether a solution of nitrate is conductor of electricity or not

Ans: (a) Third period

(b) A (NO₃) ₂

(c) Conductor of electricity

 

 

9. The ionic radii of alkaline earth metals are smaller than those of alkali metals. Why?

Ans: Effective nuclear charge increases so the radius of alkaline earth metal decreases.