Question

Which one of the following has pyramidal shape?
(1) NH3
(2) SiF4
(3) H2O
(4) BF3​

Answer 1

Answer:

(1)NH₃ -Trigonal pyramidal shape.

₇N - 1s² 2s² 2p³

₁H - 1s¹

only valence shell electrons will participate in bonding like in N only 2s² and 2p³ (5e⁻) orbitals and in H, 1s¹ (1e⁻) orbital can take part in bonding.

bond angle in NH₃ is 107°

Answer 2

The correct option is 1.

• The electronic configuration of N in ammonia is
• ${1s}^{2} {2s}^{2} {2p}^{3}$
• The valance shell of N is 2s and 2p. Total valance electrons are 5. The three H atoms participate in bonding with N and two electrons reside as lone pairs on the N atom. Thus $NH_3$ possesses a pyramidal shape.
• The electronic configuration of Si in silicon fluoride is
• ${1s}^{2} {2s}^{2} {2p}^{6}3s^23p^2$
• The valance shell of Si is 3s and 3p. Total valance electrons are 4. The four F atoms participate in bonding with Si. Thus $SiF_4$ possesses a tetrahedral shape.
• The electronic configuration of O in water is
• ${1s}^{2} {2s}^{2} {2p}^{4}$. The valance shell of O is 2s and 2p. Total valance electrons are 6. The two H atoms participate in bonding with O and four electrons reside as lone pairs on the O atom. Thus $H_2O$ possesses a bent or angular shape.
• The electronic configuration of B in boron trifluoride is
• ${1s}^{2} {2s}^{2} {2p}^{1}$. The valance shell of B is 2s and 2p. Total valance electrons are 3. The three F atoms participate in bonding with B . Thus $BF_3$ possesses a trigonal planner shape.