Question

In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later

• A. Germanium
• B. Chlorine
• C. Oxygen
• D. Silicon

Answer 1

The correct option is A

Germanium

The explanation for the correct answer:

Option (A): Germanium

Mendeleev's Periodic Table:

• In Mendeleev's periodic table the elements were arranged on the basis of their fundamental property, the atomic mass, and also on the similarity of chemical properties.
• Therefore were $63$ elements known at that time.
• $63$ elements were arranged in the increasing order of their atomic masses and found that the elements with similar chemical properties occur at regular intervals.
• The periodic law states that the properties of elements are a periodic function of their atomic masses.

Predicted Elements

• The periodic table predicted the existence of those elements which were yet to be discovered.
• These pre-predicted elements were named Eka-boron, Eka-aluminium, and Eka-silicon.
• After their discovery, they were named Scandium$\left(\mathrm{Sc}\right)$, Gallium$\left(\mathrm{Ga}\right)$, and Germanium$\left(\mathrm{Ge}\right)$, respectively.

Properties of Eka-aluminium and Gallium
	Property	Eka-aluminium	Gallium
1.	Atomic mass	68	69.7
2.	Formula of Oxide	${\mathrm{E}}_2{\mathrm{O}}_3$	${\mathrm{Ga}}_2{\mathrm{O}}_3$
3.	Formula of Chloride	${\mathrm{ECl}}_3$	${\mathrm{GaCl}}_3$

The explanation for the incorrect answer:-

Option (B): Chlorine

• Chlorine was already included in Mendeleev's periodic table.
• Hence it is the incorrect option.

Option (C): Oxygen

• Oxygen also was already included in Mendeleev's periodic table.
• Hence it is the incorrect option.

Option (D): Silicon

• Germanium was discovered later, which matched the properties set by Mendeleev and was placed in his periodic table.
• However, Silicon was already present in the periodic table.
• hence it is the incorrect option.

Hence, the correct answer is option (A).