Classification of Elements and Periodicity in Properties - Online Test
Q1. The outer electronic configuration of f - Block elements are:
Answer : Option C
Explaination / Solution:
The two rows of elements at the bottom of the Periodic Table, called the Lanthanoids, Ce(Z = 58) – Lu(Z = 71) and Actinoids, Th(Z = 90) – Lr (Z = 103) are characterised by the outer electronic configuration (n-2)f1-14 (n-1)d0-1ns2. The last electron added to each element is filled in f- orbital.
Q2. The correct order for the increase in atomic radii is
Answer : Option D
Explaination / Solution:
In a group movig from top to bottom the number of shells increases. So the atomic size increases. Although the effective nuclear charge increases but its effect is negligible in comparison to the effect of increasing number of shells.
Q3. The correct order for the decrease in atomic radii is
Answer : Option D
Explaination / Solution:
In a period moving from left to right, the effective nuclear charge increases because the next electron fills in the same shell. So the atomic size decreases.
Q4. One of the following has ns1 as its outermost electronic configuration
Answer : Option D
Explaination / Solution:
The elements of Group 1 (alkali metals) which have ns1 outermost electronic configuration belong to the s-Block Elements.
Q5. Right order of increasing metallic character is:
Answer : Option A
Explaination / Solution:
Elements of s block are more matallic than p block elements
Q6. The elements charecterised by the filling of 4 f-orbitals, are:
Answer : Option A
Explaination / Solution:
The two rows of elements at the bottom of the Periodic Table, called the Lanthanoids, Ce(Z = 58) – Lu(Z = 71) and Actinoids, Th(Z = 90) – Lr (Z = 103) are characterised by the outer electronic configuration (n-2)f1-14 (n-1)d0-1ns2. The last electron added to each element is filled in f- orbital. These two series of elements are hence called the Inner-Transition Elements (f-Block Elements).
Q7. One of the following options is not used for explaining atomic radius
Answer : Option D
Explaination / Solution:
The distance from centre of the nucleus to the outermost shell containing the electrons is called atomic radius. There are four types that are widely used: covalent radii, metallic radii, van der Waal's radii and ionic radii.
Q8. The correct increasing order of atomic radii for the same element is ----?
Answer : Option D
Explaination / Solution:
For the same element ,
- Metallic radius of atoms are always greater than corresponding covalent radius.
- Metallic radius is always lesser than van der Waal's radius
Hence , the correct increasing order of atomic radii of an element is
Q9. Which one of the following molecules represents the increasing order of bond length ?
Answer : Option C
Explaination / Solution:
The bond lengths depend upon the number and type of bonds present in a molecule . Greater the number of bonds shorter would be the bond length.
Thus , the given molecules are all diatomic molecules where ,
(i) has the smallest bond length as it is triple bonded.
(ii) is double bonded so its bond length is greater than .
(iii) both , though single bonded , the bond length of is greater than that of due to its larger atomic size.
Hence , the correct increasing order of given molecules is
Q10. Choose one of the following in the increasing order of electron gain enthalpy
Answer : Option C
Explaination / Solution:
In general as the we move down the group electron gain enthalpy decreases; so the expected trend should be I < Br < Cl < F but in actual the order is I < Br < F < Cl . This is due to small size of F atom. The valence electrons of F atom provide strong repulsion to incoming electron, hence F has unexpectedly low electron affinity.
