Assertion & Reason Test: Periodic Classification of Elements - 2


12 Questions MCQ Test Online MCQ Tests for Class 10 | Assertion & Reason Test: Periodic Classification of Elements - 2


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Attempt Assertion & Reason Test: Periodic Classification of Elements - 2 | 12 questions in 24 minutes | Mock test for Class 10 preparation | Free important questions MCQ to study Online MCQ Tests for Class 10 for Class 10 Exam | Download free PDF with solutions
QUESTION: 1

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : According to Mendeleev, the properties of elements are a periodic function of their atomic masses.

Reason : Atomic number is equal to the number of protons.

Solution: According to Mendeleev, periodic properties of elements are periodic functions of their atomic weight.

According to Moseley's periodic law, periodic properties of elements are periodic functions of their atomic number.

Hence, the Assertion is incorrect.

Atomic number is equal to the number of protons. It is also equal to the number of electrons. The mass number is equal to the sum of the number of protons and the number of neutrons.

Hence, the Reason is correct.

QUESTION: 2

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Nitrogen has higher ionization energy than that of oxygen.

Reason : Nitrogen has a smaller atomic size than that of oxygen.

Solution: Nitrogen has higher ionisation energy as it has stable half filled orbital structure.
QUESTION: 3

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Be, Mg and Ca can be classified as Dobereiner’s triads.

Reason : Atomic mass of Mg is approximately the average of the sum of atomic masses of Be and Ca.

Solution: Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

According to the Dobereiner’s triads, the three elements in a triad were arranged in the order of increasing atomic masses, the atomic mass of the middle element was roughly the average of the atomic masses of the other two elements. So, taking Be, Mg and Ca as a triad.

Elements

Be

Mg

Ca

Atomic mass

9

24

40

Average atomic mass of first and third element

9 + 40 / 2 = 24.5

QUESTION: 4

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
Assertion : Boron has a smaller first ionisation enthalpy than beryllium.
Reason : The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.  

Solution:

Boron has a smaller first ionisation enthalpy than beryllium because the penetration of a 2s electron to the nucleus is more than the 2p- electrons. Hence, 2p electron is more shieleded by the inner core of electron than the 2s electron.

QUESTION: 5

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Group 1 (1s) elements are known as the alkali elements.

Reason : s-orbital can accommodate only two electrons.

Solution: Assertion: Group I (1s) elements are known as the alkali elements as they form oxides and hydroxides which combine with water to form alkali. Alkali word is derived from the Arabic word 'alquis' which means plant ashes which are rich in sodium carbonate and potassium carbonate.

Reason: According to Pauli’s exclusion principle, an ss orbital contains at most two electrons with the opposite spin (up and down).

s−orbital can accommodate only two electrons. A p orbital can accommodate six electrons and d orbital can accommodate 10 electrons.

Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

QUESTION: 6

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : In triad, the three elements have the same gaps of atomic masses.

Reason : Elements in a triad have similar properties

Solution: In the Doberiener's triad, all three elements have similar properties and the atomic weight of the middle member of each triad is very close to the arithmetic mean (average) of the other two elements.

The Dobereiner's triads include (1) Li, Na, K (2) Ca, Sr, Ba and (3) Cl, Br, I.

QUESTION: 7

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Mendeleev’s arranged elements in horizontal rows and vertical columns.

Reason : Mendeleev’s ignored the order of atomic weight thinking that the atomic measurements might be incorrect

Solution: Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Mendeleev’s arranged elements in horizontal rows and vertical columns. He ignored the order of atomic weight thinking that the atomic measurements might be incorrect and placed the elements with similar properties

QUESTION: 8

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Fluorine has greater atomic radius than nitrogen.

Reason : Atomic radius decreases along a period.

Solution: Atomic radius is defined as the distance from the centre of the nucleus of an atom to the outermost shell of electrons. The atomic radius decreases along a period. In moving from left to right across the period, the charge on the nucleus increases by one unit (due to increase in atomic number), but the additional electron goes to the same shell. As a result, outer electrons are pulled in closer to the nucleus. This causes the decrease of atomic size.
QUESTION: 9

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Smaller the size of an atom, greater is the electronegativity.

Reason : Electronegativity refers to the tendency of atom to share electrons with other atom

Solution: Electronegativity refers to the tendency of atom to attract bonding electrons.
QUESTION: 10

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Elements in the same vertical column have similar properties.

Reason : Elements have periodic dependence upon the atomic number.

Solution: Properties of an element mostly depends on their valence shell configuration. Elements in the same group have similar outer electronic configuration and therefore similar chemical properties.
QUESTION: 11

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Noble gases are highly reactive.

Reason : Noble gases have stable closed shell electronic configuration.

Solution: Inert gases (noble gases) are very less reactive due to stable closed shell electronic configuration like ns2, np6 or ns2.
QUESTION: 12

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : The highest I.E. in a period is shown by noble gas.

Reason : Noble gases are at the extreme right of the period.

Solution: Both assertion and reason are true but reason is not the correct explanation of assertion.

Noble gases have completely filled electron shells and very stable electron configuration.

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