Tag: the periodic table

Questions Related to the periodic table

An inert gas which is not very soluble in water?

chemistry the periodic table periodic trends in chemical properties alkali metals study of specific groups

  1. $Ne$

  2. $Ar$

  3. $Xe$

  4. $CO _2$

  5. $He$

Show answer
Correct Option: E
Explanation:

Helium is an inert gas. Inert gases are not very reactive as their outermost shell is completely filled. $ {He} $ is not very soluble in water.

Thus option $E$ is the correct answer.

Choose the correct answer:

As per the octet rule, noble gases are stable in nature. This is due to the presence of________ electrons in their outermost shell.

chemistry the periodic table periodic trends in chemical properties alkali metals study of specific groups

  1. 8

  2. 18

  3. 6

  4. 2

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Correct Option: A
Explanation:

As per octet rule, noble gases have 8 electrons in their outermost shell. According to octet rule the element which has 8 electron in its valence shell are stable.

According to the law of triads :

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

  1. the properties of the middle element were in between those of the other two members.

  2. three elements arranged according to increasing weights have similar properties.

  3. the elements can be grouped in the groups of six elements.

  4. every third element resembles the first element in periodic table.

Show answer
Correct Option: A
Explanation:

According to Dobereiner's law of triads, the properties of the middle element were in between those of the other two members. The elements were arranged in a group of three (called triads). The atomic weight of a middle element was almost the average of the other two. Three elements of the triad had similar chemical properties.

The law of triad is applicable to a group of :

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

  1. $Cl, Br, I$

  2. $C, N, O$

  3. $Na, K, Rb$

  4. $H, O, N$

Show answer
Correct Option: A,B
Explanation:

For Dobereiner's triads, the atomic weight of middle element is almost average of other two. Thus, the law of triad is applicable to (1) $Cl, Br, I$ and (2) $C, N, O$. However, it is not applicable to (3) $Na, K, Rb$ and (4) $H, O, N$. 


(1) For $Cl, Br$ and $I$, $\displaystyle \dfrac {35.5+127}{2} = 81.25 \simeq 80$ 


(2) For $C, N, O$ $\displaystyle \dfrac {12+16}{2}=14$ 

(3) For $Na, K, Rb$ $\displaystyle \dfrac {23+85.5}{2}=54.25 \neq 39$ 

(4) For $H,O,N$ $\displaystyle \dfrac {1+14}{2}=7.5 \neq 14$

In Doberenier triads, the atomic weights of the elements in a triad are in increasing order.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

True, atomic weight of the element in a Doberenier traid is in increasing order. Example: LI, Na, and K with atomic weight 6, 23, and 39 respectively.

Example of Dobereiner's triad is _________.

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

  1. $Li , Al , Ca$

  2. $Li , Na , K$

  3. $Li , K , Na$

  4. $K , Al , Ca$

Show answer
Correct Option: B
Explanation:

$Li,Na,K$ is the example of Dobereineer's traid. Here, average of atomic weights of  'Li' and 'K' equals atomic weight of 'Na'.


$\dfrac{Weight\ of\ Li+ weight\ of\ K}{2}$ =$\dfrac{7+39}{2}$ =$\dfrac{46}{2}$ =23


=weight of $Na$.

The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. Such an arrangement of elements called as :

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

  1. Dobereiner triad.

  2. Mendeleev triad.

  3. Modern triad.

  4. none of the above.

Show answer
Correct Option: A
Explanation:

Dobereiner observed in few atoms that mass of one atom is equal to the average of two atoms. He defined almost all properties basing on atomic weight.Later on it was proved wrong any-ways. Hence, this is called Dobereiner triad. Lithium has 7, sodium has 23 where as potassium has 39 as atomic masses.
$ 23 = (7+39)/2 = 23$

Here, we could observe that sodium atomic mass is average of potassium and lithium masses. 

The law of triads was given by :

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

  1. Dobereiner

  2. Lewis

  3. Mendeleev

  4. Dalton

Show answer
Correct Option: A
Explanation:

In the year 1829, Johann Wolfgang Dobereiner, a German scientist, was the first to classify elements into groups based on John Dalton's assertions. He grouped the elements with similar chemical properties into clusters of three called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element. When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was approximately the arithmetic mean of the other two elements of the triad.

If the two members of a Dobereiner's triad are chlorine and iodine, then the third member of this triad is :

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

  1. fluorine

  2. bromine

  3. sodium

  4. calcium

Show answer
Correct Option: B
Explanation:

According to Dobereiner, the atomic mass of the middle element is nearly equal to the arithmetic mean of the other two. Therefore, the atomic mass of the third element is $=$ $\dfrac{{35.5}+{127}}{2}$ $=$ 81.25, which is the atomic mass of bromine.

If the two members of a Dobereiner triad are phosphorus and antimony, the third member of this triad is :

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

  1. arsenic

  2. sulphur

  3. iodine

  4. calcium

Show answer
Correct Option: A
Explanation:

According to Dobereiner, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two. Therefore, the atomic mass of the third element is $=$ $\frac{{31}+{121.75}}{2}$ $=$ 76.37 which is nearly equal to the atomic mass of arsenic.