The element with atomic number 12 is: MCQ with Answer and Explanation

The element with atomic number 12 is:
A. Potassium
B. Sodium
C. Aluminium
D. Magnesium
Answer: Option D
Solution (By JKSSB Mock Tests)
Atomic number 12 = magnesium (Mg). Electronic configuration 2,8,2. It belongs to Group 2, Period 3. Sodium is 11, aluminium 13, potassium 19.

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More chemistry Questions

Question #1
The number of atoms in a molecule of phosphorus (P₄) is:
A. 2
B. 4
C. 1
D. 8

Correct Answer: Option B


Explanation:
White phosphorus exists as P₄ tetrahedral molecules, containing 4 phosphorus atoms. So atomicity is 4. Sulfur is S₈, oxygen is O₂, ozone O₃. Atomicity is the number of atoms in a molecule of an element. Phosphorus is a non-metal. Red phosphorus is polymeric but P₄ is the common molecular form.

This question belongs to: Science chemistry
Question #2
Hardness of water is mainly caused by the presence of dissolved salts of:
A. Calcium and Magnesium
B. Iron and Zinc
C. Copper and Lead
D. Sodium and Potassium

Correct Answer: Option A


Explanation:
Water hardness is primarily caused by the presence of dissolved multivalent cations, most commonly calcium (Ca²⁺) and magnesium (Mg²⁺) ions, usually in the form of bicarbonates, chlorides, or sulfates. Sodium and potassium salts do not cause hardness.

This question belongs to: Science chemistry
Question #3
In the extraction of aluminium from bauxite, the reagent used to remove silica as an impurity is:
A. CO
B. Cl₂
C. NaOH
D. HCl

Correct Answer: Option C


Explanation:
Bauxite contains SiO₂ (silica) as impurity. In the Bayer's process, powdered bauxite is treated with hot concentrated NaOH solution. Alumina dissolves forming sodium aluminate (NaAlO₂), while silica does not dissolve and is filtered off. Alternatively, silica can be removed by adding lime during refining. The purified alumina is then electrolyzed in cryolite. NaOH selectively dissolves Al₂O₃ due to its amphoteric nature.

This question belongs to: Science chemistry