IGCSE Chemistry Paper-1: Specimen Questions with Answers 68 - 69 of 99

Which of the following describes the correct Lewis dot structure for magnesium chloride.

Answer

b.

Explanation

Magnesium whose atomic number is 12, has 2, 8, 2 configuration. So, it has two electrons in its valence shell. The electronic configuration of chlorine (At. no. 17) is 2,8,7. So it has seven valence electrons. Since, magnesium has two electrons in excess of the neon configuration

(2, 8) , and chlorine is one electron short of the argon configuration (2,8,8) , hence one atom of magnesium will transfer its two electrons to two atoms of chlorine (one to each) as shown below:

An oxidation reaction takes place when copper powder kept in a china plate is heated. A black coating is formed on the surface of copper. What product is formed in the above reaction?

Answer

b.

Explanation

Following reaction will take place when copper will be heated.

2Cu + O₂ 2CuO

Therefore copper oxide is formed.