Question

Prelab Assignment You are asked by your instructor to draw the Lewis structure of the NHCI molecule. Being of a conservative nature, you proceed as directed in the Procedure section. 1. First, find the number of valence electrons in NHECI. For counting purposes with Lewis structures, the number of valence electrons in an atom of a main group clement is equal to the last digit in the group number of that element in the Periodic Table. N is in Group ; H is in Group : Cl is in Group In NHCl there is a total of valence electrons. 2. Assemble a skeleton structure for the molecule, connecting the N, H's, and Cl to make one unit. Use the rule that N atoms typically form three bonds, whereas Cl and H atoms usually form only one. The Natom, listed first in the formula, will be the central atom. How many 3. How many electrons did you need to make the skeleton structure? electrons are left over? 4. If your model is to obey the octet rule, each atom must have four electron pairs (except for hydrogen atoms, which need and can only have one electron pair). Complete your Lewis structure below with the remaining electrons, which can be represented as nonbonding electron pairs around the atoms. 5. Describe the molecular geometry of NH3CI (Refer to a table of molecular geometries for this question) 6. Is the NHCl molecule polar? Why? 7. Would you expect NHCl to have any isomeric forms? Would NH CI have any resonance structures? _Explain your reasoning. If so, draw them below.

Answer 1

1.

the number of valence electrons in an atom is equal to the last digit in the group number of the periodic table. (valid for only s and p block elements)

• N is in the 15th group; The Valence electrons will be 5.
• H is in 1st group; The Valence electrons will be 1.
• Cl is in the 17th group; The Valence electron will be 7.

therefore, the total valence electron in NH₂Cl = 5+1+7= 13.

2.

Nitrogen typically forms 3 covalent bonds whereas, Cl and H forms one covalent bond. The central atom, nitrogen will be forming a tetrahedral geometry comprising of 3 covalent bonds and one lone pair.

        °°

N

/     /    \ 1 lone pair of N and 3 lone pair of Cl.

H   H       Cl

3.  

The Valence electrons of N is 5. The Valence electrons of H is 1. The Valence electron of Cl is 7.

in which, 3 valence electrons of N participate with 1 valence electron of H and Cl each. thus a total of 6 electrons is needed to form the NH₂Cl skeleton. And 8 electrons are leftover. ( 1 lone pair of N and 3 lone pair of Cl)

4.

°°

N

/     /    \ { Non-Bonding Electrons are called lone pairs: 1 lone pair of N and 3 lone pair of Cl }

H   H       Cl  °°

°° °°