Periodic Classification of Elements Test

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Periodic Classification of Elements Test - 19

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Weekly Quiz Competition

Question 1
1 / -0

As we move along a period, the valency of elements :

A
increases

B
decreases

C
remains same

D
increases in the beginning and then decreases

Solution

On moving across a period the number of electrons increases but as the valence electrons crosses $$4$$ it is easier for elements to accept electrons. So the valency decreases.
Hence, option $$D$$ is correct.
Question 2
1 / -0

What is the valency of magnesium with atomic number $$12$$?

A
$$2$$

B
$$4$$

C
$$5$$

D
$$6$$

Solution

The electronic configuration of magnesium is $$2,\,8,\,2$$. The valence shell contains $$2$$ electrons. Therefore the valency is two.
Question 3
1 / -0

_________ were not included in Mendeleev's periodic table.

A
Alkali metals

B
Isotopes

C
Halogens

D
Non-metals

Solution

Mendeleev's table was based on the atomic masses of elements. There were some limitations of Mendeleev's periodic table as:
It could not explain the position of hydrogen in the table.
No position for isotopes was given.
Isotopes were discovered long after Mendeleev's periodic table. Isotopes of an element have similar chemical properties, but different atomic masses.
Question 4
1 / -0

Which of the following statements are correct about Mendeleev's periodic table?
i) It is based on increasing order of atomic numbers.
ii) Mendeleev corrected the atomic weight of some elements like Be, In etc.
iii) $$(Ar , H_{2} ), (Co, Cl_{2}), (Te, F_{2})$$ are three inverted pairs.
iv) It is based on increasing order of atomic weights.

A
only (i) correct

B
(ii) and (iv) are correct

C
only (iii) correct

D
(i) and (iv) are correct

Solution

Mendeleev's periodic table is based on the increasing order of atomic weights.
It follows the periodic law which states that the physical and chemical properties of elements are a periodic function of their atomic weights.
Hence, statement (i) is incorrect and (iv) is correct.
Mendeleev corrected the atomic weight of some elements like Be, In, Au, Pt, etc based on their position in the periodic table.
For example, the atomic mass of beryllium was corrected from $$13.5$$ to $$9$$. Hence, statement (ii) is correct.
The inverted pairs are ($$Ar, K$$), ($$Co, Ni$$) and ($$Te$$, $$I_2$$). They are also called anomalous pairs. Their positions are not justified.
Hence, the statement (iii) is incorrect.
Question 5
1 / -0

Which among the following elements has the largest atomic radii?

A
$$Na$$

B
$$Mg$$

C
$$K$$

D
$$Ca$$

Solution

The atomic radii increase down the group and decrease across a period.

Among the given options, the atomic radii will increase in the following order: $$Mg<Na<Ca<K$$.
Question 6
1 / -0

Upto which element, the law of octaves was applicable?

A
Oxygen

B
Calcium

C
Cobalt

D
Potassium

Solution

The law of octaves was found to be applicable till calcium. After calcium, the properties of the next elements were not synchronous as per the law of octaves.
Question 7
1 / -0

Number of short periods in Mendeleev's periodic table is :

A
$$2$$

B
$$3$$

C
$$4$$

D
$$1$$

Solution

Period number 1, 2 and 3 contain 2, 8 and 8 elements respectively. Other periods contain more than 8 elements. Hence, the first three periods are called as short periods. So, total of 3 short periods are there in Mendeleev periodic table.
Question 8
1 / -0

The properties of _________ were predicted by Mendeleev before their isolation.

A
Co and Ni

B
I and Te

C
Sc, Ga and Ge

D
Cl, Ar and K

Solution

Mendeleev has the foresight to leave some gaps in the periodic table for 3 elements and these elements are discovered later and included in the table.

Those three elements are:
1) Eka-boron is presently known as scandium ($$\text{Sc}$$).
2) Eka-silicon is presently known as germanium ($$\text{Ge}$$).
3) Eka-aluminium is presently known as gallium($$\text{Ga}$$).

Hence, the correct option is $$\text{C}$$
Question 9
1 / -0

In Mendeleev's periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later?

A
Germanium

B
Chlorine

C
Oxygen

D
Silicon

Solution

Chlorine, oxygen and silicon were included in Mendeleev's periodic table. Germanium was discovered later which fit into the empty spaces left by Mendeleev and matched to the expected properties.
Question 10
1 / -0

Mendeleev corrected the atomic weight of :

A
$$Be$$

B
$$N$$

C
$$O$$

D
$$Cl$$

Solution

Mendeleev's periodic table helped in correcting the atomic masses of some of the elements, based on their positions in the periodic table. For example, the atomic mass of beryllium was corrected from 13.5 to 9.0. Atomic masses of indium, gold and platinum were also corrected.

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Periodic Classification of Elements Test - 19

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Periodic Classification of Elements Test - 19

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Question 1

increases

decreases

remains same

increases in the beginning and then decreases

Solution

Question 2

$$2$$

$$4$$

$$5$$

$$6$$

Solution

Question 3

Alkali metals

Isotopes

Halogens

Non-metals

Solution

Question 4

only (i) correct

(ii) and (iv) are correct

only (iii) correct

(i) and (iv) are correct

Solution

Question 5

$$Na$$

$$Mg$$

$$K$$

$$Ca$$

Solution

Question 6

Oxygen

Calcium

Cobalt

Potassium

Solution

Question 7

$$2$$

$$3$$

$$4$$

$$1$$

Solution

Question 8

Co and Ni

I and Te

Sc, Ga and Ge

Cl, Ar and K

Solution

Question 9

Germanium

Chlorine

Oxygen

Silicon

Solution

Question 10

$$Be$$

$$N$$

$$O$$

$$Cl$$

Solution

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