5 Most VSAQ’s of Classification of Elements – The Periodic Table Chapter in Class 10th Physical Science (TS/AP)

2 Marks

VSAQ-1 : Why lanthanoids and actinoids placed separately at the bottom of the periodic table?

  1. Distinct Properties: Lanthanoids and actinoids are placed separately due to their unique and distinct properties compared to other elements.
  2. Valence Electrons: The distinction arises because the valence electrons in these elements enter into the 4f and 5f orbitals for lanthanoids and actinoids, respectively.
  3. Characteristic Properties: This electron configuration leads to a wide range of characteristic properties that differentiate them from other elements.

VSAQ-2 : State Moseley’s periodic law.

Statement of Moseley’s Periodic Law

Moseley’s periodic law asserts that “The physical and chemical properties of elements are a periodic function of their atomic numbers” rather than their atomic weights.

Significance of Moseley’s Law

  1. This law was a significant advancement in understanding the periodic table.
  2. It led to the rearrangement of elements based on atomic numbers (the number of protons in the nucleus).
  3. This understanding was pivotal in developing the modern structure of the periodic table.

VSAQ-3 : State Dobereiner’s law of triads.

Dobereiner’s Law of Triads states that “When three elements with similar properties are arranged in ascending order of their atomic weights, the atomic weight of the middle element is approximately the average of the atomic weights of the first and third elements.”

VSAQ-4 : What is valency of an element?

Definition of Valency:

Valency is the ability of an element’s atom to combine with atoms of other elements to form chemical compounds.

Example of Valency:

The valency of an oxygen atom is 2, indicating it can combine with two hydrogen atoms to form water (H2O).

VSAQ-5 : An element has atomic number 17. Where would you expect this element in the periodic table and why?

Electronic Configuration and Position:

  1. An element with atomic number 17 has the electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁵.
  2. Based on its outermost electron configuration (3p⁵), this element belongs to the 3rd period and the 17th group (VIIA) of the periodic table.

Reason for Placement:

  1. Elements in the same group have similar valence electron configurations, leading to similar chemical properties.
  2. Therefore, an element with atomic number 17 is placed in this position due to its specific electron configuration.