Periodicity in the properties of elements in modern periodic table is due to:
Periodicity in the properties of elements in modern periodic table is due to:
The correct option is B Periodicity in the electronic configuration of atom of elements
Periodicity
The occurrence of similar properties in elements after certain regular intervals when arranged in the increasing order of their atomic numbers is called periodicity. Due to the periodicity of properties, the elements of the same group have similar properties. Therefore, periodicity can be described as the regular periodic variation of elements' properties across a period and down a group in the modern periodic table.
Explanations for wrong answers
(A) Atomic weight increases with the increase in the atomic number of the elements. Though it can explain the regular increase in some of the properties of elements with atomic numbers, it cannot explain the similar properties of elements of the same group. Therefore, option (A) is incorrect.
(C) The atomic number gives the number of electrons and protons in the atom. Therefore, it can explain the effect of nuclear charge on the size of the atom. But it cannot explain the difference in properties across a period and down a group. Therefore, option (C) is incorrect.
(D) In the modern periodic table, each family refers to each group. The elements of each family will have the same properties. But the periodicity is not due to the existence of families of elements but families exist due to the periodicity in properties. Therefore, option (D) is incorrect.
Explanation for correct answer
(B) Each shell in an atom has a maximum occupancy. Due to this, after one shell is completely filled, the electrons are filled in the outer shell, causing a periodicity in the number of electrons in the outer shell or its electronic configuration. The chemical properties of an element depend on its valency. Since the valency will be the same for elements with similar electronic configuration, the periodicity of properties occurs due to the periodicity in electronic configuration.
The correct answer is (B) Periodicity in the electronic configuration of atom of elements.
Periodicity in the electronic configuration of atom of elements
Periodicity
The occurrence of similar properties in elements after certain regular intervals when arranged in the increasing order of their atomic numbers is called periodicity. Due to the periodicity of properties, the elements of the same group have similar properties. Therefore, periodicity can be described as the regular periodic variation of elements' properties across a period and down a group in the modern periodic table.
Explanations for wrong answers
(A) Atomic weight increases with the increase in the atomic number of the elements. Though it can explain the regular increase in some of the properties of elements with atomic numbers, it cannot explain the similar properties of elements of the same group. Therefore, option (A) is incorrect.
(C) The atomic number gives the number of electrons and protons in the atom. Therefore, it can explain the effect of nuclear charge on the size of the atom. But it cannot explain the difference in properties across a period and down a group. Therefore, option (C) is incorrect.
(D) In the modern periodic table, each family refers to each group. The elements of each family will have the same properties. But the periodicity is not due to the existence of families of elements but families exist due to the periodicity in properties. Therefore, option (D) is incorrect.
Explanation for correct answer
(B) Each shell in an atom has a maximum occupancy. Due to this, after one shell is completely filled, the electrons are filled in the outer shell, causing a periodicity in the number of electrons in the outer shell or its electronic configuration. The chemical properties of an element depend on its valency. Since the valency will be the same for elements with similar electronic configuration, the periodicity of properties occurs due to the periodicity in electronic configuration.
The correct answer is (B) Periodicity in the electronic configuration of atom of elements.
