Question

A, B and C are elements of Dobereiner’s triad. If the atomic mass of A is 7 and that of C s 23, what will be the atomic mass of B.

Answer 1

ɢɪᴠᴇɴ :-

A, B and C are elements of Dobereiner’s triad. If the atomic mass of A is 7 and that of C is 23.

ᴛᴏ ғɪɴᴅ :-

• Mass of element B

sᴏʟᴜᴛɪᴏɴ :-

➤ According to Dᴏʙᴇʀᴇɪɴᴇʀ ,

• The atomic mass of the central element was merely the arithmetic mean of atomic mass of the other two elements.

Mass of :-

A = 7

B = ?

C = 23

So,

We get,

➥ Arithmetic mean of A and B = (A + B) / 2

➭ (7 + 23)/2

➭ 30/2

➭ 15

Hence,

• Atomic mass of element B is 15

Answer 2

${ \green{ \boxed{ \underline{ \mathtt{Question}}}}}$

Elements A, B and C occurs as Dobereiner's triads. If the atomic mass of A is 7 and that of C is 23, what will be the atomic mass of B?

${ \green{ \boxed{ \underline{ \mathtt{Answer}}}}}$

Dobereiner's triads follow a specific pattern. That is,

When the mass of first and last element is added and if that sum is divided by two, we get the mass of Middle element. This is considered as the average atomic mass of A and C will give the approximate mass of B.

So,

A = 7, C = 23

➟$b = \frac{a + c}{2}$

➟ $b = \frac{7 + 23}{2}$

➟$b = \frac{30}{2}$

➟${ \boxed{ \mathtt{15}}}$

Hence the atomic mass of B is 23.

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