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प्रश्न
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उत्तर
The necessary conditions for the formation of covalent molecule are:
Number of valence electrons: Both the participating atoms should have four or more valence electrons in their valence shell.
Equal electro negativities: The combining atoms should have equal electro negativities so that no transfer of electrons takes place.
Equal electron affinities: The combining atoms should also have equal electron affinities i.e. equal attraction for electrons.
Ionization energy: It should be high for both the atoms so that there is no chance of removal of electrons.
High nuclear charge and small inter nuclear distance: Both these conditions favor the formation of covalent bond because during the formation of a covalent bond the electron density gets concentrated between the nuclei of the combining atoms and this electronic charge is responsible for holding the two nuclei together.
The properties of covalent compounds are:
Nature: They are generally volatile liquids or gases. Some may be gases like urea, sugar etc.
Low melting and boiling points: Since the intermolecular forces of attraction are weak, very small amount of heat energy is required to overcome these forces hence their melting and boiling points are low.
Electrical conductivity: Since covalent compounds are made up of molecules and not ions, so they do not conduct electricity.
Solubility: These are insoluble in water but soluble in organic solvents.
Ionization in solution: These do not ionize when dissolved in water except some polar covalent compounds like HCl.
Molecular reactions: These participate in reactions as a molecule so the reactions are called molecular reactions. These are slow reactions.
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संबंधित प्रश्न
What type of bonds are present in CO2 molecule? Draw their electron-dot structures.
Why is graphite used for making dry cell electrodes but diamond is not?
The atomic numbers of four elements P, Q, R and S are 6, 10, 12 and 17 respectively. Which two elements can combine to form a covalent compound?
(a) P and R
(b) Q and S
(c) P and S
(d) R and S
Give two example in following case:
Gaseous polar compounds
In the formation of electrovalent compounds, electrons are transferred from one element to another. How are electrons involved in the formation of a covalent compound?
Fill in the blank with correct word from the bracket.
Melting and boiling points of covalent compounds are generally ______ (low, high).
Which of the following is a common characteristic of a covalent compound?
Draw an electron dot diagram to show the formation of the following compound.
Methane
"Carbon prefers to share its valence electrons with other atoms of carbon or with atoms of other elements rather than gaining or losing the valence electrons in order to attain noble gas configuration." Give reasons to justify this statement.
The electron dot structure of chlorine molecule is:
