Dobernier's Triads

Q. The atomic mass of lithium (Li) and sodium (Na) are 7 u and 23 u respectively. If lithium, sodium, and potassium form Dobereiner's triad, what is the atomic mass of potassium (K)?

1. 15 u
2. 8 u
3. 39 u
4. 30 u

Q.

Which of the following groups follows Dobereiner’s law of triads?

1. Br, Cl, I
2. Cl, Br, I
3. Li, K, Na
4. Sr, Ba, Ca

Q. Calcium, strontium, barium form a Dobereiner's triad. The atomic masses of calcium and barium are 40 u and 137 u respectively. Predict the atomic mass of strontium.​

1. 60 u​
2. 90 u
3. 88 u
4. 63.7 u

Q.

Which of the following triads is a Dobereiner's Triad?

1. Na, Ra, Al

2. S, O, H

3. Li, Na, K

4. N, P, As

Q.

In Dobereiner's triads, when three elements in a triad are written in the increasing order of atomic masses; the atomic mass of the middle element is roughly the average of the atomic masses of the other two elements. Identify ‘X’ from the given triad.
Li (6.9), Na (X), K (39.0)

1. 15.3

2. 19.0

3. 45.9

4. 23.0

Q.

Identify the missing elements from the following Dobereiner's triads.

1. Mg, Al, F

2. Si, P, Te

3. Li, Sr, I

Q.

The elements in the Dobereiner’s Triads follow: –

1. The elements are written in increasing order of atomic mass.

2. The mass of middle element was roughly the average of atomic masses of other two elements.

3. Elements in the Triads show similar properties.

4. All the options are correct

Q. Given below are the elements with their atomic masses. Identify a set of elements which is not a Dobereiner Triad?

1. Li (6.9), Na (23.0), K (39.0)
2. N (14.0), P (31.0), As (74.9)
3. Ca (40.1), Sr (87.6), Ba (137.3)
4. Cl (35.5), Br (79.9), I (126.9)

Q.

Which of the following can form Dobereiner’s Triads: with Li(m = 6.9) and Na(m = 23)?

1. K (m = 32)

2. K (m = 37)

3. K (m = 45)

4. K (m = 39)

Q. ntTriad-I [N3-, O2-, Na+]n ntTriad-II [N+, C+, O+]n ntChhose the species of lowest ionization potential from Triad-I and highest IP from Triad-II respectivelyn nt(a) N3-, O+n nt(b)N3-, N+n

Q. In Dobereiner's triads, when three elements in a triad are written in the increasing order of atomic masses; the atomic mass of the middle element is roughly the average of the atomic masses of the other two elements. Identify ‘X’ from the given triad.
Li (6.9), Na (X), K (39.0).

1. 15.3
2. 19.0
3. 23.0
4. 45.9

Q.

In a Dobereiner’s triad, the respective atomic masses of the first and the last elements are 40 and 137

What is the mass of the middle element of the triad?

1. 177

2. 128

3. 49

4. 88

Q. How did Dobereiner made his periodic table in the form of triad or the form of the table

Q.

In dobereiner classification of elements, the atomic weight of the middle element is equal to the mean of the atomic weight of the extreme elements.

1. True
2. False

Q. Three elements X, Y and Z form a Dobereiner triad. The atomic weights of X and Z is in the ratio 5 :17. If the sum of the atomic weights of extreme elements is 176, then find the atomic weights of Y.

1. 88
2. 60
3. 80
4. 90

Q.

State Dobereiners law of triads for the classification of elements. Support your answer by two examples.

Q.

In Dobereiner's triad, elements showed similarities in _______ .

1. Atomic masses

2. Properties

3. Decomposition

4. Atomic number

Q. A, B, C are three elements forming Dobereiner's triad. If the atomic mass of A and C are in the ratio 3:4 and sum of their atomic masses is 27 then find the atomic mass of B.

Q.

‘X’, ‘Y’ and ‘Z’ belong to II-A group and obey the Dobereiners Law of triads. Identify the true statement regarding X, Y and Z.

1. $\mathrm{X}\to \mathrm{Ca},\mathrm{Y}\to \mathrm{Sr},\mathrm{Z}\to \mathrm{Ba}$, and $\mathrm{Ba}$ is a good reducing agent.

2. $\mathrm{X}\to \mathrm{Mg},\mathrm{Y}\to \mathrm{Ca},\mathrm{Z}\to \mathrm{Sr}$, and $\mathrm{Ca}$ is a good reducing agent.

3. $\mathrm{X}\to \mathrm{Mg},\mathrm{Y}\to \mathrm{Ca},\mathrm{Z}\to \mathrm{Sr}$, and $\mathrm{Mg}$ has low I.P. value.

4. $\mathrm{X}\to \mathrm{Ca},\mathrm{Y}\to \mathrm{Sr},\mathrm{Z}\to \mathrm{Ba}$, and $\mathrm{Mg}$ has lower I.P. value than that of X, Y and Z.

Q. In Dobereiner's triads, when three elements in a triad are written in the increasing order of atomic masses; the atomic mass of the middle element is roughly the average of the atomic masses of the other two elements. Identify ‘X’ from the given triad.
Li (6.9), Na (X), K (39.0)

1. 15.3
2. 23.0
3. 19.0
4. 45.9

Q.

Given elements X, Y and Z with atomic masses a, b and c are said to form Dobereiner's triad. Which of the following statement is true if its known that a > b > c?

1. $b\approx \frac{a-c}{2}$

2. $b\approx 2a-c$

3. $b\approx \frac{3c+a}{2}$

4. $b\approx \frac{c+a}{2}$

Q. Which of the following groups follows Dobereiner's Law of Triads?

1. Sr, Ba, Ca

2. Br, Cl, I

3. Cl, Br, I

4. Li, K, Na

Q. The elements in the Dobereiner's Triads follow: -

1. The elements are written in increasing order of atomic mass

2. The mass of middle element was roughly the average of atomic masses of other two elements

3. Elements in the Triads show similar properties.

4. All of these

Q. In the Doberiener's triad, all three elements have similar:

1. properties
2. electronic configuration
3. number of shells
4. both A and B

Q.

A, B & C are the elements of the Dobereiner's triads. If the atomic mass of A is 7 and that of C is 23, then the atomic mass of B will be __.

Q.

If three elements X. Y and Z form a triad and atomic weights of X and Z are $9$ and $40$, respectively, then the atomic weight of an element Y is

Q.

A, B & C are the elements of the Dobereiner's triads. If the atomic mass of A is 7 and that of C is 23, then the atomic mass of B will be __.

Q.

Question 2
What were the limitations of Dobereiner's classification?