Question

Define symbol and valency​

Answer 1

Answer:

A chemical symbol is a notation of one or two letters representing an atom of a chemical element.

A symbol plays a significant role in the study of elements. For e.g. the symbol Cl represents:

The element chlorine

One atom of chlorine

The atomic mass of chlorine i.e.,17 a.m.u

Valency indicates the combining capacity of an atom or radical. It is defined as the number of hydrogen atoms that will combine with or displace one atom of that element or radical.

Metals are electropositive in nature and lose electrons to attain octet configuration. Metals in Group 1 (alkali metals) have one valence electron and are univalent.

Metals in group 2 (alkaline earth metals) have 2 valence electrons and are divalent.

Metals in group 3 have 3 valence electrons and are trivalent.

o Na – e– ⇨ Na+ (univalent).

o Ca – 2e– ⇨ Ca2+ (divalent).

o Al – 3 e– ⇨ Al3+ (trivalent).

Non-metals are electronegative in nature and gain electrons to attain octet configuration.

o Cl + e– ⇨ Cl– (univalent).

o O + 2e– ⇨ O2- (divalent).

o N + 3e– ⇨N3-(trivalent).

Carbon, silicon and other group four elements have four valence electrons. They are called tetravalent elements. Under normal conditions, these elements share electrons with one or more other elements to gain octet configuration.

However, Sn4+ and Pb4+ also exist.

Answer 2

Explanation:

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• A chemical symbol denotes in short, a particular element or an atom of that element. ... Valency is the combining capability of an element. In other words, the number of electrons which an atom can gain or share or lose when a chemical reaction takes place defines its valency.

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