Question

4. How does a covalent bond form ? Show the formation of nitrogen molecule (N2). How are melting and boiling points, and electrical conductivity of covalent compounds different from those of ionic compounds

Answer 1

First image Source: Google

Covalent Compounds

Second Image Source: Google

Ionic Compounds

Third Image Source: Google

Covalent bond Form

Question:-

How does a covalent bond form?

Answer:

The" sharing" of electrons between two non-metal elements.

Covalent bonding arises from the fundamental idea that all elements want to achieve a stable configuration of an outer shell consisting of 8 electrons.

This can be achieved in different ways, but in the case of covalent bonding 2 atoms "share" their electrons with the other atom. This is especially seen among the halogens (group 7/17) where all the elements are said to be diatomic as they are made up of 2 atoms bonded together by covalent bonding. e.g Cl2.

On it's own each atom from a group 7/17 elements would have 7 valence electrons, but as they "share" they have a full shell which is much more stable.

Note that this type of bondings is only possible between two elements considered as non-metals (between a metal and a non-metal the bond would be ionic) .Another famous example would be Carbon, which has 4 valence electrons. Methane, CH4, is a carbon atom covalently bonded to 4 separate hydrogen atoms!

In the diagram below you see that the crosses are the atoms that "belong" to the Carbon atom and the dots are atom belonging to the hydrogens, but they share them.

Covalent Compounds

Covalent bonds are characterized by the sharing of electrons between two or more atoms. These bonds mostly occur between nonmetals or between two of the same (or similar) elements.Two atoms with similar electronegativity will not exchange an electron from their outermost shell; the atoms instead share electrons so that their valence electron sb shell is filled.

Examples of compounds that contain only covalent bonds are methane (CH4), carbon monoxide (CO), and iodine monobromide (IBr).

Covalent bonding between hydrogen atomsSince each hydrogen atom has one electron, they are able to fill their outermost shells by sharing a pair of electrons through a covalent bond.

Ionic Compounds

Ionic bonding occurs when there is a large difference in electronegativity between two atoms. This large difference leads to the loss of an electron from the less electronegative atom and the gain of that electron by the more electronegative atom, resulting in two ions. These oppositely charged ions feel an attraction to each other, and this electrostatic attraction constitutes an ionic bond.

Ionic bonding occurs between a nonmetal, which acts as an electron acceptor, and a metal, which acts as an electron donor. Metals have few valence electrons, whereas nonmetals have closer to eight valence electrons; to easily satisfy the octet rule, the nonmetal will accept an electron donated by the metal. More than one electron can be donated and received in an ionic bond.

Some examples of compounds with ionic bonding include NaCl, KI, MgCl2.

Formation of sodium fluoride (NaF)The transfer of an electron from a neutral sodium atom to a neutral fluorine atom creates two oppositely charge ions: Na+ and F–. Attraction of the oppositely charged ions is the ionic bond between Na and F.

Answer 2

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Covalent bond is formed by the Sharing of electrons between atoms to acquire stable electronic configuration.

Example : N₂ molecule

Two Nitrogen atoms with 5 valence electrons and still require 3 more electrons to attain octet. So , the two nitrogen atoms form three covalent bonds between them so that the both atoms acquire octet.

$\cdot$ N ≡ N

The covalent compunds posses low melting and boiling points due to weak vanderwaal forces of attraction , where as the ionic compounds posses high melting and boiling points due to strong vanderwaal's forces of attraction because of prescence of oppositely charged ions. Mostly covalent compounds do not conduct electricity . Ionic compounds do not conduct electricity in solid state due to the tight package of ions where as ionic compounds conduct electricity in molten state due to the free movement of ions.