Question

(a) Explain the formation of ionic compound CaO with electron dot structure. Atomic number of calcium and oxygen are 20 and 8 respectively.
(b) Name the constituent metals of bronze.


CBSE Class X Science SA 2 (3 Marks)

Answer 1

K L M N. K L M N

Ca. 2 8 8 2 O 2 6

Ca: + O×××××× = (Ca-2)( O:××××××)

*The (=) represents the pointing to the right in an chemical equation

*The (×) which represent the electrons are surrounding O along with (:)

Answer 2

Answer:

Bronze exists as a metal alloy consisting primarily of copper usually with tin as the main additive. It exists hard and brittle.

Explanation:

(a) Calcium reacts with oxygen to create an ionic compound calcium oxide (CaO). The atomic number of calcium exists at 20 and that of oxygen exists at 8.

By losing two electrons, the calcium atom constitutes a calcium ion $\left(\mathrm{Ca}^{2+}\right)$, and by acquiring two electrons, the oxygen atom forms an oxide ion $\left(\mathrm{O}^{2}\right.)$. The calcium ion has 2 units of positive charge whereas the oxide ion has 2 units of a negative charge, which are held together by a strong electrostatic force of attraction to create a calcium oxide compound $\mathrm{Ca}^{2+} \mathrm{O}^{2-}$. Thus calcium oxide has ionic bonds. The electron dot representation for the formation of calcium oxide exists shown below:

(b) Bronze exists as a metal alloy consisting primarily of copper usually with tin as the main additive. It exists hard and brittle.

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