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# The Atomic Numbers of Three Elements A, B and C Are Given Below: Element Atomic Number A 5 B 7 C 10 (I) Which Element Belongs to Group 18? (Ii) Which Element Belongs to Group 15? (Iii) Which Element Belongs to Group 13? (Iv) to Which Period/Periods Do These Elements Belong? - CBSE Class 10 - Science

ConceptPosition of Elements and Trends in the Modern Periodic Table

#### Question

The atomic numbers of three elements A, B and C are given below:

 Element Atomic number A 5 B 7 C 10

(i) Which element belongs to group 18?
(ii) Which element belongs to group 15?
(iii) Which element belongs to group 13?
(iv) To which period/periods do these elements belong?

#### Solution

(i) Element C belongs to group 18.
Electronic configuration of element C (10) = 2,8
Therefore, group number = valence shell + 10
= 8+10 = 18.

(ii) Element B belongs to group 15.
Electronic configuration of element B (15) = 2,8,5
Therefore, group number = valence shell + 10
= 5+10 = 15.

(iii) Element A belongs to group 13.
Electronic configuration of element A (5) = 2,3
Therefore, group number = valence shell + 10
= 3+10 = 13.

(iv) The elements A, B and C all belong to period 2 because all three have the same valence shell, i.e, L.

Is there an error in this question or solution?

#### APPEARS IN

Lakhmir Singh Solution for Chemistry for Class 10 (2019 Exam) (2018 to Current)
Chapter 5: Periodic Classification Of Elements
Q: 61 | Page no. 306

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Solution The Atomic Numbers of Three Elements A, B and C Are Given Below: Element Atomic Number A 5 B 7 C 10 (I) Which Element Belongs to Group 18? (Ii) Which Element Belongs to Group 15? (Iii) Which Element Belongs to Group 13? (Iv) to Which Period/Periods Do These Elements Belong? Concept: Position of Elements and Trends in the Modern Periodic Table.
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