Tag: the periodic table

Quizzes (8) Questions (146)

Questions Related to the periodic table

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Which of the following statements is not true about Dobereiner's law of triads?

  1. The law was applicable to all known elements

  2. Nitrogen family does not obey the law of triads

  3. Dobereiner's classification was not very useful

  4. The atomic mass of the central element of each triad was merely the arithmetic mean of of the atomic masses of other two elements
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Döbereiner’s triads could find only three triads; .i.e total of 9 elements only but there were many more elements known at that time.

Therefore Dobereiner’s could not classify most of the elements known at that time.

Hence, the correct option is $A$
Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

In a triad of $A, B, C$ elements if the atomic masses of $A$ and $C$ respectively are $100$ and $200$, then the atomic mass of $B$ is:

  1. $300$
  2. $175$
  3. $125$
  4. $150$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to Dobereiner's law of traid, the average of the masses of the first and the last element is equal to the atomic mass of the middle element. So, $\dfrac{100+200}{2}$ = 150. Hence, the atomic mass of B is 150.


Hence, the correct option is $\text{D}$

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

In Doberenier triads, the atomic weights of the elements in a triad are in increasing order.
State whether the given statement is true or false.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In 1829, Dobereiner proposed the Law of Triads: Middle element in the triad had the atomic weight that was the average of the other two members. Soon other scientists found chemical relationships extended beyond triads. Fluorine was added to Cl/Br/I group; sulfur, oxygen, selenium, and tellurium were grouped into a family; nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another group. In a group, those were in increasing order of atomic weight. Hence, the statement is true.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

When a Dobereiner's triad is considered, the sum of atomic weights of the terminal elements $X$ and $Z$ is 162.5. The atomic weight of $Z$ is 50 units less than 5 times that of $X$. Identify the periods of $X, Y$ and $Z$ respectively in the present periodic table.

  1. $3,4,5$
  2. $4,5,6$
  3. $2,3,4$
  4. $3,5,4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the atomic weights (in g/mol) of elements X, Y and Z be x, y and z respectively.
The atomic weight of Z is 50 units less than 5 times that of X.

$\displaystyle z = 5x-50$.....(1)

The sum of atomic weights of the terminal elements X and Z is 162.5
$\displaystyle x+z=162.5$
$\displaystyle z = 162.5-x$......(2)

Substitute (2) into (1)
$\displaystyle 162.5-x=5x-50$
$\displaystyle 162.5=6x-50$
$\displaystyle 6x=212.5$
$\displaystyle x=35.4$ g/mol

Substitute this in equation (2)
$\displaystyle z = 162.5-x = 162.5-35.4=127.1$ g/mol.

The atomic weight of Y is the arithmetic mean of the atomic weights of X and Z.
$\displaystyle y = \dfrac {x+z}{2}$
$\displaystyle y = \dfrac {35.4+127.1}{2}=81.3$ g/mol.

From the periodic table, we see that the elements with atomic weights 35.4, 81.3 and 127.1 belong to 3 (chlorine), 4 (bromine) and 5 (iodine).

Hence, the option (A) is the correct answer.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Which is mismatched regarding the position of the elements as given below?

  1. X(Y=89), f - block, 6th period

  2. Y(Z=100), f - block, 7th period

  3. Z(Z=115), d - block, 7th period

  4. Both (1) & (3)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Element with Z=89 (Actinium) is in the f-block (or d-block depending on convention, but usually d-block start) and 7th period. Z=100 (Fermium) is f-block, 7th period. Z=115 (Moscovium) is p-block, 7th period. The question asks for the mismatch, and since multiple entries are incorrect, D is the intended answer.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Electronic configuration of silver atom in ground state.

  1. $\left[ Kr \right] { 3d }^{ 10 }{ 4s }^{ 1 }$
  2. $\left[ Xe \right] { 4f }^{ 14 }{ 5d }^{ 10 }{ 6s }^{ 1 }$
  3. $\left[ Kr \right] { 4d }^{ 10 }{ 5s }^{ 1 }$
  4. $\left[ Kr \right] { 4d }^{ 9 }{ 5s }^{ 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electronic configuration of $Ag$ in ground state is:$[Kr]4d^{10}5s^1$