Question

question 9
what is the shape of the species shown in the lewis structure below?
o=n-cl (with lone pairs as shown in the image)
options: bent, linear, octahedral, see saw, square planar, square pyramid, tetrahedral, trigonal bipyramid, trigonal planar, trigonal pyramid, t-shape

Explanation:

Step1: Determine the central atom

The central atom here is N (nitrogen).

Step2: Calculate the number of valence electrons around N

- O contributes 2 electrons (double bond), Cl contributes 1 electron (single bond), and we need to check the lone pairs on N. Let's calculate the formal charge or the number of electron groups.
- The Lewis structure: O is double bonded (1 double bond = 2 electron groups), Cl is single bonded (1 electron group), and we need to check the lone pairs on N. Wait, let's do the electron - group calculation properly.
- The formula for electron - group geometry: count the number of bonding groups and lone pairs around the central atom.
- For N in \( \text{NOCl} \) (the species here, let's confirm the formula: O = N - Cl). The central N atom:
- Bonding groups: 2 (double bond with O, single bond with Cl)
- Lone pairs: Let's calculate the valence electrons. N has 5 valence electrons. O (double bond) contributes 2 electrons (from the double bond, but actually, in terms of electron groups, a double bond is 1 electron group), Cl (single bond) contributes 1 electron group. Wait, maybe a better way: use the VSEPR theory.
- The number of electron groups around N: double bond (1 group), single bond (1 group), and lone pairs. Let's calculate the formal charge on N. Formal charge = valence electrons - non - bonding electrons - \( \frac{1}{2} \) bonding electrons.
- Valence electrons of N: 5.
- Non - bonding electrons: Let's see the Lewis structure. The N has one lone pair? Wait, no. Wait the Lewis structure drawn: O has two lone pairs, N has one lone pair? Wait, let's count the electrons.
- O: 6 valence electrons, in the double bond, it uses 4 (2 in each bond), so it has 2 lone pairs (4 electrons).
- Cl: 7 valence electrons, in the single bond, it uses 1, so it has 3 lone pairs (6 electrons).
- N: 5 valence electrons. It forms a double bond (4 electrons) with O and a single bond (2 electrons) with Cl. So total bonding electrons: 4 + 2 = 6. Non - bonding electrons: 5 - 3 (since \( \frac{6}{2}=3 \) bonding electrons "used" from N's valence) = 2? Wait, maybe I'm overcomplicating. Let's use VSEPR: the electron - group geometry is determined by the number of electron groups (bonding + lone pairs) around the central atom.
- For \( \text{NOCl} \), the central N atom has:
- Bonding groups: 2 (double bond with O, single bond with Cl)
- Lone pairs: 1 (because 5 - (4 + 2)/2=5 - 3 = 2? Wait, no. Wait the correct way: the number of electron groups (steric number) = number of bonding atoms + number of lone pairs on central atom.
- For N in \( \text{NOCl} \):
- Number of bonding atoms: 2 (O and Cl)
- Number of lone pairs: Let's calculate the number of non - bonding electrons on N. The total number of electrons around N: from the bonds, O - N double bond (4 electrons) and N - Cl single bond (2 electrons), so total bonding electrons around N: 6. N has 5 valence electrons, so non - bonding electrons: 5 - 3 (since \( \frac{6}{2}=3 \) bonding "units") = 2, which is 1 lone pair (2 electrons).
- So steric number (electron - group number) = 2 + 1 = 3.
- Electron - group geometry for steric number 3 is trigonal planar. But the molecular geometry (shape) is determined by the number of bonding groups and lone pairs. Here, bonding groups = 2, lone pairs = 1. So the molecular geometry is bent? Wait, no. Wait steric number 3: electron - group geometry is trigonal planar. If there is 1 lone pair and 2 bonding groups, the molecular geometry is bent? Wait, no, wait:
- Steric number 3:
- 3 bonding groups, 0 lone pairs: trigonal planar.
- 2 bonding groups, 1 lone pair: bent? Wait, no, actually, when steric number is 3, and there is 1 lone pair and 2 bonding groups, the shape is bent? Wait, no, let's take an example. \( \text{SO}_2 \): steric number 3 (2 bonding groups, 1 lone pair), shape is bent. But in our case, the central atom N in \( \text{NOCl} \):
- Wait, maybe I made a mistake in the steric number. Let's re - calculate.
- The correct way: count the number of electron domains (bonding and non - bonding) around the central atom.
- A double bond is one electron domain, a single bond is one electron domain, and a lone pair is one electron domain.
- In \( \text{NOCl} \), N is bonded to O (double bond, 1 domain), bonded to Cl (single bond, 1 domain), and has one lone pair (1 domain). So total electron domains = 3.
- Electron - domain geometry: trigonal planar.
- Molecular geometry: since there is 1 lone pair and 2 bonding domains, the molecular geometry is bent? Wait, no, wait: when electron - domain geometry is trigonal planar (3 domains) and the number of bonding domains is 2 and lone pairs is 1, the molecular geometry is bent? Wait, no, actually, the correct shape for 2 bonding domains and 1 lone pair in a trigonal planar electron - domain geometry is bent? Wait, no, let's check the VSEPR table.
- VSEPR table:
- Steric number (SN) = number of electron domains.
- SN = 3:
- Bonding domains (BD) = 3, Lone pairs (LP)=0: trigonal planar.
- BD = 2, LP = 1: bent (angular).
- BD = 1, LP = 2: linear (but not our case).
- But wait, in the case of \( \text{NOCl} \), the central N atom:
- Wait, maybe I messed up the lone pair. Let's re - draw the Lewis structure. The correct Lewis structure for \( \text{NOCl} \): N is in the middle. O is double - bonded (O = N), Cl is single - bonded (N - Cl). The N has one lone pair. So electron domains: O = N (1), N - Cl (1), and lone pair (1). So 3 electron domains.
- So molecular geometry: with 2 bonding domains and 1 lone pair, the shape is bent? Wait, no, wait another example: \( \text{ClO}_2^- \): but no, let's go back.
- Wait, the correct shape for \( \text{NOCl} \) is bent? Wait, no, actually, the correct shape is bent? Wait, no, I think I made a mistake. Wait, let's calculate the steric number again.
- Valence electrons of N: 5, O: 6, Cl: 7.
- Total valence electrons: 5 + 6+7 = 18.
- In the Lewis structure: O = N - Cl. O has two lone pairs (4 electrons), Cl has three lone pairs (6 electrons), N has one lone pair (2 electrons). Let's check the total electrons: double bond (4 electrons) + single bond (2 electrons) + O's lone pairs (4) + Cl's lone pairs (6) + N's lone pair (2) = 4 + 2+4 + 6+2 = 18, which matches.
- So around N: electron domains: double bond (1), single bond (1), lone pair (1). So 3 electron domains.
- Electron - domain geometry: trigonal planar.
- Molecular geometry: the number of bonding domains is 2 (O and Cl), lone pair is 1. So the molecular geometry is bent? Wait, no, when there are 3 electron domains (trigonal planar) and 1 lone pair, the molecular geometry is bent? Wait, no, the correct term for 2 bonding domains and 1 lone pair in trigonal planar electron - domain geometry is bent. But wait, another way: the bond angles. In a trigonal planar electron - domain geometry, the ideal bond angle is \( 120^{\circ} \), but with a lone pair, the bond angle between the two bonding domains will be less than \( 120^{\circ} \), and the shape is bent.
- Wait, but let's check the options. The options include "bent" and "trigonal planar". Wait, no, the options are: bent, linear, octahedral, see saw, square planar, square pyramid, tetrahedral, trigonal bipyramid, trigonal planar, trigonal pyramid, T - shape.
- Wait, maybe I made a mistake in the number of lone pairs on N. Let's re - examine the Lewis structure. The N in the structure: O = N - Cl. Let's count the electrons around N. O is double - bonded (so N - O has 4 electrons), N - Cl has 2 electrons. So total bonding electrons around N: 6. N has 5 valence electrons, so non - bonding electrons: 5 - 3 (since \( \frac{6}{2}=3 \)) = 2, which is 1 lone pair. So electron domains: 3 (2 bonding, 1 lone pair). So molecular geometry is bent? Wait, no, trigonal planar electron - domain, 2 bonding, 1 lone pair: bent. But wait, the correct shape of \( \text{NOCl} \) is actually bent? Wait, no, I think I was wrong. Wait, the correct shape of \( \text{NOCl} \) is bent? Wait, no, let's check the VSEPR theory again.
- The formula for molecular geometry:
- If the central atom has 3 electron domains (trigonal planar electron - domain geometry) and:
- 3 bonding domains: trigonal planar.
- 2 bonding domains and 1 lone pair: bent (angular).
- 1 bonding domain and 2 lone pairs: linear.
- So in our case, 2 bonding domains (O and Cl) and 1 lone pair on N, so the molecular geometry is bent. But wait, another source: \( \text{NOCl} \) has a bent molecular geometry? Wait, no, actually, \( \text{NOCl} \) has a trigonal planar electron - domain geometry and a bent molecular geometry? Wait, no, I think I made a mistake. Wait, the correct shape of \( \text{NOCl} \) is actually bent? Wait, no, let's calculate the steric number again. Wait, maybe the N has no lone pair? Wait, no, the Lewis structure: O = N - Cl. Let's count the formal charge on N. Formal charge = 5 - (2 (non - bonding) + \( \frac{6}{2} \) (bonding)) = 5 - (2 + 3)=0. So non - bonding electrons on N: 2 (1 lone pair). So electron domains: 3. So molecular geometry: bent.

Step3: Match with the options

The option "bent" is available. But wait, wait, maybe I made a mistake. Wait, let's check again. Wait, the central atom N: electron domains: double bond (1), single bond (1), lone pair (1). So 3 electron domains. Molecular geometry: bent. So the correct answer is bent.

Answer:

bent