Periodic Classification of Elements

Periodic Classification of Elements

• Options:
  a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
  c) Assertion (A) is true, but Reason (R) is false.
  d) Assertion (A) is false, but Reason (R) is true.

 

Question 1

Assertion (A): The periodic table is arranged in order of increasing atomic number.
Reason (R): Atomic number is more fundamental than atomic mass for classifying elements.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The modern periodic table is based on atomic numbers because it provides a more accurate representation of elemental properties than atomic mass.

Question 2

Assertion (A): Elements in the same group of the periodic table have similar chemical properties.
Reason (R): Elements in the same group have the same number of valence electrons.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The similar number of valence electrons among elements in the same group leads to similar reactivity and chemical behavior.

Question 3

Assertion (A): The size of atoms generally decreases across a period.
Reason (R): Increased nuclear charge pulls the electrons closer to the nucleus.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: As you move across a period, the number of protons increases, which increases the positive charge of the nucleus, attracting the electron cloud and reducing atomic size.

Question 4

Assertion (A): Noble gases are chemically inert.
Reason (R): Noble gases have a complete octet of electrons in their outermost shell.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The full outer shell of electrons in noble gases makes them stable and unreactive under normal conditions.

Question 5

Assertion (A): Transition metals exhibit variable oxidation states.
Reason (R): Transition metals have d-orbitals that can accommodate different numbers of electrons.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The availability of d-orbitals allows transition metals to lose different numbers of electrons, leading to various oxidation states.

Question 6

Assertion (A): The reactivity of alkali metals increases down the group.
Reason (R): As atomic size increases, the outermost electron is held less tightly.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The increase in atomic size down the group reduces the effective nuclear charge experienced by the outermost electron, making it easier to lose that electron.

Question 7

Assertion (A): Chlorine is more reactive than fluorine.
Reason (R): Chlorine has a larger atomic size than fluorine.

• Answer: b) Assertion (A) is false, but Reason (R) is true.
• Explanation: While chlorine is larger, fluorine is more reactive due to its high electronegativity and smaller atomic size, which allows it to attract electrons more effectively.

Question 8

Assertion (A): The first ionization energy increases across a period.
Reason (R): The effective nuclear charge increases, making it harder to remove an electron.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The increase in nuclear charge as you move across a period results in a stronger attraction between the nucleus and the electrons, requiring more energy to remove an electron.

Question 9

Assertion (A): Metalloids have properties of both metals and non-metals.
Reason (R): Metalloids can conduct electricity but are brittle like non-metals.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Metalloids, located between metals and non-metals on the periodic table, exhibit a mix of metallic and non-metallic properties, such as electrical conductivity and brittleness.

Question 10

Assertion (A): Atomic radius increases down a group.
Reason (R): Additional electron shells are added as you move down a group.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Each subsequent element in a group has an additional electron shell, leading to an increase in atomic radius.

Question 11

Assertion (A): All elements in group 1 are soft and can be cut with a knife.
Reason (R): They have a single valence electron that makes them highly reactive.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The presence of one valence electron makes alkali metals soft and gives them high reactivity, allowing them to easily lose that electron.

Question 12

Assertion (A): Elements with similar properties are found in the same period.
Reason (R): Elements in the same period have the same number of electron shells.

• Answer: b) Assertion (A) is false, but Reason (R) is true.
• Explanation: While elements in the same period have the same number of electron shells, similar properties are found in groups, where elements share the same number of valence electrons.

Question 13

Assertion (A): The metallic character of elements decreases across a period.
Reason (R): Non-metals are found on the right side of the periodic table, while metals are on the left.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: As we move from left to right across a period, the elements transition from metals to non-metals, resulting in a decrease in metallic character.

Question 14

Assertion (A): The chemical reactivity of non-metals increases down the group.
Reason (R): The ability of non-metals to gain electrons decreases down the group.

• Answer: b) Assertion (A) is false, but Reason (R) is true.
• Explanation: Non-metals generally become less reactive down the group because the increased atomic size makes it harder for them to gain electrons.

Question 15

Assertion (A): Boron and aluminum are both classified as metalloids.
Reason (R): Both elements have properties of metals and non-metals.

• Answer: b) Assertion (A) is false, but Reason (R) is true.
• Explanation: While boron is classified as a metalloid, aluminum is actually classified as a metal, although it does exhibit some properties of metalloids.

Question 16

Assertion (A): Iodine has a higher electronegativity than chlorine.
Reason (R): Electronegativity decreases down a group in the periodic table.

• Answer: b) Assertion (A) is false, but Reason (R) is true.
• Explanation: Electronegativity does decrease down a group; thus, chlorine has a higher electronegativity than iodine due to its smaller atomic size.

Question 17

Assertion (A): Group 17 elements are called halogens.
Reason (R): Halogens are known for forming salts with metals.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The term "halogen" means "salt-former," reflecting the ability of these non-metals to react with metals to form ionic compounds (salts).

Question 18

Assertion (A): Lanthanides and actinides are placed below the main periodic table.
Reason (R): They have unique electron configurations that require additional space in the periodic table.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: The unique properties and electron configurations of lanthanides and actinides lead to their placement in separate rows below the main periodic table to maintain order and organization.

Question 19

Assertion (A): Alkali metals react vigorously with water to produce hydrogen gas.
Reason (R): The reactivity of alkali metals increases down the group.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Alkali metals react with water to form hydroxides and hydrogen gas, and this reaction becomes more vigorous as you move down the group.

Question 20

Assertion (A): The noble gas configuration is a stable arrangement for all elements.
Reason (R): Atoms strive to achieve a noble gas configuration to attain stability.

• Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
• Explanation: Atoms tend to lose, gain, or share electrons to achieve a stable electron configuration similar to that of noble gases, which have a complete outer shell.