Assertion and Reason Questions for Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties

Home » CBSE Class 11 Chemistry » Assertion Reason Questions for Class 11 Chemistry » Assertion and Reason Questions for Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties

Directions : Each of these questions contain two statements, Assertion and Reason. Each of these questions also has four alternative choices, only one of which is the correct answer. You have to select one of the codes (a), (b), (c) and (d) given below.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Q.1. Assertion : Second period consists of 8 elements.
Reason : Number of elements in each period is four times the number of atomic orbitals available in the energy level that is being filled.

Answer Answer: (c) Number of elements in each period is twice the number of atomic orbitals available in the energy level that is being filled.

Q.2. Assertion : In a triad, the three elements present have same gaps of atomic masses.
Reason : Elements in a triad have similar properties.

Answer Answer:(d) In a triad, the atomic mass of the middle element is the mean of the atomic masses of the first and third elements.

Q.3. Assertion : Smaller the size of an atom greater is the electronegativity.
Reason : Electronegativity refers to the tendency of atom so share electrons with other atom.

Answer Answer: (c) Assertion is true but reason is false.
Electronegativity refers to the tendency of atom to attract bonding electrons.

Q.4. Assertion : According to Mendeleev, periodic properties of elements is a function of their atomic number.
Reason : Atomic number is equal to the number of protons.

Answer Answer: (d) According to Mendeleev, periodic properties of elements is a function of their atomic masses.

Q.5. Assertion : Atomic number of the element ununbium is 112.
Reason : Name for digits 1 and 2 is un- and bi-respectively in latin words.

Answer Answer: (a) Both assertion and reason are true and reason is the correct explanation of assertion.

Q.6. Assertion : Hydrogen can be placed in group 1.
Reason : Hydrogen can gain an electron to achieve a noble gas arrangement.

Answer Answer: (b) Both the statements are correct but assertion is not correct explanation for reason.

Q.7. Assertion : Atomic size increases along a period.
Reason : Effective nuclear charge increases as the atomic number increases resulting in the increased attraction of electrons to the nucleus.

Answer Answer: (c) Atomic size generally decreases along a period

Q.8. Assertion : Second ionization enthalpy will be higher the first ionization enthalpy.
Reason : Ionization enthalpy is a quantitative measure of the tendency of an element to lose electron.

Answer Answer: (b) Both assertion and reason are true but reason is not the correct explanation of assertion.
It is difficult to remove an electron from a positively charged ion than a neutral atom.

Q.9. Assertion : Alkali metals have least value of ionization energy within a period.
Reason : They precede alkaline earth metals in periodic table.

Answer Answer: (b) Both assertion and reason are true but reason is not the correct explanation of assertion.
Alkali metals belong to first group and have largest size in a period and hence low I.E.

Q.10. Assertion : Helium is placed in group 18 along with p-block elements.
Reason : It shows properties similar to p-block elements.

Answer Answer:(c) He (1s2) should be placed along with s-block elements because of its electronic configuration but it has a completely filled valence shell and as a result it exhibits properties of noble gases, thus it is placed along with noble gases (ns2, np6).

Q.11. Assertion : Electron gain enthalpy can be exothermic or endothermic.
Reason : Electron gain enthalpy provides a measure of the ease with which an atom adds an electron to form anion.

Answer Answer: (b) Both assertion and reason are true but reason is not the correct explanation of assertion.
Depending on the element, the process of adding an electron to the atom can be either endothermic or exothermic.

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