Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following questions with explanation:
a. 3Li, 14Si, 2He, 11Na, 15P
Which of these elements belong to the period 3?
→ Let's wrtie the electronic configurations:
3Li: 2, 1
14Si: 2, 8, 4
2He: 2
11Na: 2, 8, 1
15P: 2, 8, 5
Among these elements
14Si (2, 8, 4), 11Na (2, 8, 1) and 15P (2, 8, 5) have three electron shells. Hence, these elements belong to the period 3.
3 Marks
b. 1H, 7N, 20Ca, 16S, 4Be, 18Ar
Which of these elements belong to the second group?
→ Let's write the electronic configurations:
1H: 1
7N: 2, 5
20Ca: 2, 8, 8, 2
16S: 2, 8, 6
4Be: 2, 2
18Ar: 2, 8, 8
Among these elements, 20Ca (2, 8, 8, 2) and 4Be (2, 2) have 2 electrons in their outermost shell. Therefore, 20Ca and 4Be belong to the second group.
3 Marks
c. 7N, 6C, 8O, 5B, 13Al
Which is the most electronegative element among these?
→ Let's write the electronic configurations:
7N: 2, 5
6C: 2, 4
8O: 2, 6
5B: 2, 3
13Al: 2, 8, 3
Electronegativity increases as we move from left to right in a period. Also, electronegativity decreases as we move down the group. Considering these two aspects, 8O (2, 6) is the most electronegative element among the given elements.
3 Marks
d. 4Be, 6C, 8O, 5B, 13Al
Which is the most electropositive element among these?
→ Let's write the electronic configurations:
4Be: 2, 2
6C: 2, 4
8O: 2, 6
5B: 2, 3
13Al: 2, 8, 3
Electropositivity decreases as we move from left to right in a period. Also, electropositivity increases as we move from top to bottom in a group. Considering these two aspects, 13Al (2, 8, 3) is the most electropositive element among the given elements.
3 Marks
e. 11Na, 15P, 17Cl, 14Si, 12Mg
Which atom is the largest?
→ Let's write the electronic configurations:
11Na: 2, 8, 1
15P: 2, 8, 5
17Cl: 2, 8, 7
14Si: 2, 8, 4
12Mg: 2, 8, 2
All these elements belong to the third period. Atomic radius goes on decreasing as we move from left to right in a period. Thus, 11Na (2, 8, 1) is the largest atom among the given elements.
3 Marks
f. 19K, 3Li, 11Na, 4Be
Which of these atoms has the smallest atomic radius?
→ Let's write the electronic configurations:
19K: 2, 8, 8, 1
3Li: 2, 1
11Na: 2, 8, 1
4Be: 2, 2
Atomic radius goes on decreasing as we move from left to right in a period. Also, atomic radius goes on increasing as we move from top to bottom in a group. Thus, the atomic radius of 4Be (2, 2) is the smallest among the given elements.
3 Marks
g. 13Al, 14Si, 11Na, 12Mg, 16S
Which of the above elements has the highest metallic character?
→ Let's write the electronic configurations:
13Al: 2, 8, 3
14Si: 2, 8, 4
11Na: 2, 8, 1
12Mg: 2, 8, 2
16S: 2, 8, 6
Metallic character means the tendency to lose electrons. All these elements belong to the third period. Metallic character goes on decreasing as we move from left to right in a period. Thus, 11Na (2, 8 1) has the highest metallic character among the given elements.
3 Marks
h. 6C, 3Li, 9F, 7N, 8O
Which of the above elements has the highest nonmetallic character?
→ Let's write the electronic configurations:
6C: 2, 4
3Li: 2, 1
9F: 2, 7
7N: 2, 5
8O: 2, 6
Nonmetallic character means the tendency to gain electrons. All these elements belong to period 2. Nonmetallic character goes on increasing as we move from left to right in a period. Thus, 9F (2, 7) has the highest nonmetallic character among the given elements.
3 Marks

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This page was last modified on
01 August 2019 at 01:45