Chemistry
State why water has two lone pairs of electrons in it's covalent molecule while ammonia has one lone pair.
Answer
Water contains two hydrogen atoms and one oxygen atom. The hydrogen atom [1] has one electron in it's valence shell while the oxygen atom [2,6] has 6 electrons in it's valence shell. Two hydrogen atom share one electron each and two unshared pairs of electrons are left as lone pairs as shown in the diagram below :
In the case of ammonia, it contains three hydrogen atoms and one nitrogen atom. Nitrogen atom [2,5] has five valence electrons and hydrogen atom [1] has one valence electron. In ammonia, each of the three hydrogen atoms are bonded to the nitrogen atom by a pair of shared electrons. Thus, the nitrogen atom in ammonia is left with one lone pair of electrons as shown in the diagram below:
Related Questions
Give reasons for formation of single covalent bond between two chlorine atoms and a double covalent bond between two oxygen atoms - during formation of a covalent chlorine molecule and formation of a covalent oxygen molecule, respectively.
Give a reason why one atom of carbon shares four electron pairs, one with each of the four atoms of chlorine during the formation of covalent molecule - carbon tetrachloride.
With the help of an atomic orbit structure diagram - explain the formation of :
(a) carbon tetrachloride
(b) methane
[at. no. : C=6, Cl=17, H=1]
Draw the atomic orbit structure diagram for formation of a -
(a) water molecule
(b) ammonia molecule
[at. no. H=1, O=8, N=7]