Question

iii) Lithium (Li),_________ and Potassium (K) is Dobereiner's triad.​

Answer 1

Answer:

Sodium (Na)

Explanation:

Lithium (Li), Sodium (Na) and Potassium (K) is Dlbereiner's triad.

Answer 2

$\huge\bf{Answer - }$

Lithium (Li), Sodium (Na), and Potassium (K) is Dobereiner's triad.

$\huge\bf{ Additional \:information - }$

• Johann Wolfgang Dobereiner was a German chemist who introduced the "law of triads".

• He introduced that if the three elements are arranged into triads then the atomic mass of the middle element is an average of the other two elements.

He introduced only three triads from all elements. They were -

1. Lithium (Li) , Sodium (Na) Potassium(K).
2. Calcium(Ca), Strontium (Sr) Barium (Ba)
3. Chlorine (Cl) , Bromine (Br) Iodine (I)

Let's understand the law of triads with an example -

1. Lithium (Li) , Sodium (Na) Potassium(K).

• The atomic mass of Lithium (Li) : 7
• The atomic mass of Sodium (Na): 23
• Atomic mass of Potassium (K) : 39

Now, $\bf{= \dfrac{7+39}{2}}$

$\bf{=\dfrac{46}{2}}$

The atomic mass of Sodium is $\bf{=23}$