Question

Predict the geometry of the following species: (a) NNO (b) \(\mathrm{ONCl}\) (c) \(\mathrm{NH}_{4}{ }^{+}\) (d) \(\mathrm{O}_{3}\)

Short answer

Answer: (a) NNO: Bent, (b) ONCl: Impossible, (c) \(\mathrm{NH}_{4}{ }^{+}\): Tetrahedral, (d) O\(_3\): Impossible

Step-by-step solution

Determine the central atom

For each species, identify the central atom, which is usually the atom with the lowest electronegativity or the one that can form the most bonds. In the given species, the central atoms are: (a) N (in NNO) (b) O (in ONCl) (c) N (in \(\mathrm{NH}_{4}{ }^{+}\)) (d) O (in O\(_3\))

Calculate the number of electron pairs

Count the number of valence electrons for the central atom and the number of electrons contributed by each bonded atom. Total these contributions and divide by 2 to find the number of electron pairs. (a) NNO: - N has 5 valence electrons. - The first N atom is double bonded to the second N atom (valence electrons: 5) and single bonded to the O atom (valence electrons: 6). - The central N atom's electron pairs: (5+5+6)/2 = 8/2 = 4. (b) ONCl: - O has 6 valence electrons. - O is single bonded to both N (valence electrons: 5) and Cl (valence electrons: 7). - The central O atom's electron pairs: (6+5+7)/2 = 18/2 = 9. (c) \(\mathrm{NH}_{4}{ }^{+}\): - N has 5 valence electrons. - It is single bonded to four H atoms (1 valence electron each). - The ion has a positive charge, indicating one fewer electron. - The central N atom's electron pairs: (5+4(1)-1)/2 = 8/2 = 4. (d) O\(_3\): - Central O has 6 valence electrons. - It is single bonded to one O (valence electrons: 6) and double bonded to another O (valence electrons: 6). - The central O atom's electron pairs: (6+6+6)/2 = 18/2 = 9.

Predict the geometry based on electron pair repulsion

Determine the arrangement of electron pairs and the molecular geometry of the species based on the number of electron pairs calculated in the previous step. (a) NNO (4 electron pairs): Tetrahedral electron pair arrangement, bent molecular geometry (as there are only three atoms in the species). (b) ONCl (9 electron pairs): Impossible - No molecular geometry can accommodate 9 electron pairs, as the maximum electron pairs surrounding an atom are 6 and it represents an octahedral electron pair arrangement. The exercise might have an error or a typo. (c) \(\mathrm{NH}_{4}{ }^{+}\) (4 electron pairs): Tetrahedral electron pair arrangement and tetrahedral molecular geometry (since all electrons are bonded). (d) O\(_3\) (9 electron pairs): Impossible - No molecular geometry can accommodate 9 electron pairs, as the maximum electron pairs surrounding an atom are 6 and it represents an octahedral electron pair arrangement. The exercise might have an error or a typo. In summary, the geometries of the given species are: (a) NNO: Bent (b) ONCl: Impossible (c) \(\mathrm{NH}_{4}{ }^{+}\): Tetrahedral (d) O\(_3\): Impossible