Question

1. Explain the term 'symbol”. State a reason why - the symbol of calcium is 'Ca' & of copper is 'Cu
2. Define the term 'valency'. With reference to water & ammonia as compounds respectively,
state the valency of oxygen & nitrogen. Magnesium [2, 8, 2] has valency 2. Give reasons.​

Answer 1

Answer:

1} Symbol is a short form for the name of an element. It is the first letter and another letter of the name of an element.

As the name of calcium and copper start with same letter of English "C" so another letter from the name of the element is added to "C".

Hence symbol of calcium is 'Ca' and symbol of copper is 'Cu'

2} Valency is the number of particular atoms combined with or displaced with another atom to form a compound.

Water which is H 2 o  two atoms of hydrogen combine with one atom of oxygen. The valency of oxygen is 2, because it needs two atoms of hydrogen to form water.

Ammonia which is NH_3  , One atom of nitrogen combines with 3 atoms of hydrogen. The valency of nitrogen is 3 because it needs 3 atoms of hydrogen to form ammonia.

Magnesium has valency equal to 2^+   because the electronic configuration of Mg is [2,8,2]. The nearest noble gas to magnesium is neon with electronic configuration of [2,8], to achieve this stable electronic configuration Mg can lose 2 valence electrons, hence its valency is 2^+.

Explanation:

Answer 2

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