Which of the following is not a Dobereiner triad -
(A) Li, Na, K
(B) Mg, Ca, Sr
(C) CI, Br, I
(D) S, Se, Te
Answers
Answer:
Which of the following is not a Dobereiner triad?
(A) Li, Na, K
(B) Mg, Ca, Sr✔✔✔
(C) CI, Br, I
(D) S, Se, Te
Explanation:
follow me Guys
Mg, Ca, Sr is not a Dobereiner triad (option-B)
- The combination of three elements, in which the average of the atomic masses of the other two elements is similar to the atomic mass of the middle element is called the Dobereiner triad.
- For example, in the case of Li, Na, and K -
- the atomic mass of Na (23g) = average of atomic masses of Li (7g) and K (39g)
- ∴ atomic mass of Na = (7 + 39) / 2
- = 46 / 2
- 23g = 23g
- Similarly S, Se, Te, and Cl, Br, I also follow the Dobereiner triad.
- Mg, Ca, and Sr do not follow the Dobereiner triad because the atomic mass of Ca (40g) is not similar to the average of the atomic masses of Mg (24g), and Sr (88g).
- the atomic mass of Ca = (atomic mass of Mg + atomic mass of Sr) / 2
- = (24+88)/ 2
- = 112 / 2
- = 56 g
- 40g = 56 g
- Therefore, Mg, Ca, and Sr do not follow the Dobereiner triad (Option-B).
- For example, in the case of Li, Na, and K -
the atomic mass of Na = average of atomic masses of Li and K
here, the atomic mass of Na = 23g
the atomic mass of Li = 7gm
the atomic mass of K = 39gm
∴ atomic mass of Na = (7 + 39) / 2
= 46 / 2
23g = 23g
- Similarly S, Se, Te, and Cl, Br, I also follow the Dobereiner triad.
- Mg, Ca, and Sr do not follow the Dobereiner triad because the atomic mass of Ca (40g) is not similar to the average of the atomic masses of Mg (24g), and Sr (88g).
the atomic mass of Ca = (atomic mass of Mg + atomic mass of Sr) / 2
= (24+88)/ 2
= 112 / 2
= 56 g
40g = 56 g
- Therefore, Mg, Ca, and Sr do not follow the Dobereiner triad (Option-B).