Naming Covalent Compounds

What are Covalent Compounds?

Covalent compounds are formed when two nonmetal atoms share valence electrons to form a covalent bond. Valence electrons are the atom’s outermost electrons. Elements want to fill their electron orbitals, or shells, with electrons, so they will form bonds with other atoms that will allow them to do so. The word ‘covalent’ is made up of the words ‘co’ (share) and ‘valent’ (valence electrons).

Formation of Covalent Bond

Elements with extremely high ionisation energies are incapable of transferring electrons, while elements with extremely low electron affinity are incapable of absorbing electrons. The atoms of such elements tend to share electrons with atoms of other elements or atoms of the same element in such a way that both atoms achieve octet configuration in their respective valence shells and thus achieve stability. A covalent Bond refers to such an association formed by the sharing of electron pairs among different or similar kinds.

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Rules for Naming Covalent Compounds

A binary compound is made up of only two elements. The names are referred to as systematic names.

The rules for naming binary covalent compounds are as follows:

  1. First, identify the element name of the nonmetal that is farthest to the left and farthest to the bottom of the periodic table.
  2. Second, use the element name for the other nonmetal, but shorten it and add a -ide ending.
  3. To indicate the number of atoms in an element, place prefixes (mono-, di-, tri-, etc.) in front of the element name. In the element formula, the number prefix corresponds to the subscript. If there is no subscript, it means that the element only has one atom, and the prefix is “mono-.” However, in the first element’s name, leave out the “mono-” prefix.

We use common names rather than systematic names for some simple covalent compounds.

Prefixes used for Covalent Compounds

Greek prefixes are used to name compounds based on the elemental subscript, which specifies the number of atoms present in the compound.

Number of Atoms in Compounds

Prefix for the element

1

mono-

2

di-

3

tri-

4

tetra-

5

penta-

6

hexa-

7

hepta-

8

octa-

9

nona-

10

deca-

Examples-

  • PCl5 – Phosphorus pentachloride
  • SO2 – Sulphur dioxide
  • CO2 – Carbon Dioxide
  • N2O5 – Dinitrogen pentoxide
  • BrF5 – Bromine pentafluoride

Naming Covalent Compounds With Three Elements

These are the rules for naming covalent compounds with three elements.

  • Specify the formula
  • Specify the charge
  • Specify the formula

For example- Na2SO4 is composed of three elements- sodium which is a cation and sulphate. Therefore, it is named sodium sulphate.

Similarly, Li4HPO4 is composed of three elements: lithium, a cation, and hydrogen phosphate. As a result, it is named lithium hydrogen phosphate.

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Solved Examples

1. Write the names of each compound-

a. CO

b. CF4

c. CCl4

Solution.

a. Carbon Monoxide

b. Carbon tetrafluoride

c. Carbon tetrachloride

2. Write the names of each compound-

a. H2O

b. CH4

c. NH3

Solution.

a. Water

b. Methane

c. Ammonia

Frequently Asked Questions on Naming Covalent Compounds

Q1

Can compounds contain both covalent and ionic bonds?

Yes, compounds can contain both covalent and ionic bonds.

For example- Na3PO4 – This compound is ionic because sodium is metal and the phosphate ion is a polyatomic ion. Polyatomic ions are held together by covalent bonds, so this compound contains both ionic and covalent bonds.

Q2

Write the molecular formula for each compound.

a. chlorine trifluoride

b. phosphorus pentachloride

The molecular formula of the following compounds are as follows-

a. ClF3

b. PCl5

Q3

How do you recognise a covalent compound?

Covalent compounds are typically made up of two or more nonmetal elements.

Q4

What are the rules for writing a simple covalent compound’s molecular formula?

It is similar to an ionic compound, except that the element further down and to the left on the periodic table is listed first and is named after the element.

Q5

What are the naming conventions for a simple covalent compound?

Name the first element first, followed by the second element, using the element name’s stem plus the suffix -ide. If there is more than one atom of the first element, use numerical prefixes; always use numerical prefixes for the number of atoms of the second element.

Test your Knowledge on Naming Covalent Compounds

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