For CH2Cl2

Determine The Total Number Of Valence Electrons. Draw A Good Lewis Structure. Calculate The Formal Charge On Each Atom In The Structure. Identify Any Resonance Structures. Name The Electronic Geometry Around The Central Atom Name The Molecular Geometry Around The Central Atom. Draw A Reasonable VSEPR Structure.

The correct answer and explanation is :

Let’s go through the steps to answer the questions about dichloromethane (CH2Cl2):

1. Total Number of Valence Electrons:

To calculate the total number of valence electrons for CH2Cl2, you need to count the electrons from each atom.

Carbon (C) is in Group 14 of the periodic table, so it has 4 valence electrons.
Hydrogen (H) is in Group 1, so each hydrogen atom has 1 valence electron. Since there are two hydrogens, this contributes 2 electrons.
Chlorine (Cl) is in Group 17, so each chlorine atom has 7 valence electrons. Since there are two chlorine atoms, this contributes 14 electrons.

Total valence electrons = 4 (C) + 2 (H) + 14 (Cl) = 20 valence electrons.

2. Lewis Structure:

Carbon (C) is the central atom, as it can form four bonds.
Place hydrogen atoms and chlorine atoms around the carbon.
To complete the octet for each chlorine atom, place a lone pair of electrons on each chlorine atom.
Hydrogen atoms will form single bonds with carbon, as they only need two electrons to complete their shell.

The structure looks like this:

    H
    |
Cl—C—H
    |
   Cl

Each line represents a pair of electrons shared in a covalent bond.

3. Formal Charge Calculation:

The formal charge (FC) is calculated using the formula:

[
FC = \text{Valence electrons} – \left( \text{Lone pair electrons} + \frac{\text{Bonding electrons}}{2} \right)
]

Let’s calculate the formal charge for each atom:

Carbon (C): Valence electrons = 4, bonding electrons = 8 (4 bonds), lone electrons = 0. FC (C) = ( 4 – \left( 0 + \frac{8}{2} \right) = 4 – 4 = 0 ).
Hydrogen (H): Valence electrons = 1, bonding electrons = 2, lone electrons = 0. FC (H) = ( 1 – \left( 0 + \frac{2}{2} \right) = 1 – 1 = 0 ).
Chlorine (Cl): Valence electrons = 7, bonding electrons = 2 (1 bond), lone electrons = 6. FC (Cl) = ( 7 – \left( 6 + \frac{2}{2} \right) = 7 – 7 = 0 ).

4. Resonance Structures:

There are no resonance structures for CH2Cl2 because there is no possibility of shifting electrons to form a different structure without breaking the octet rule.

5. Electronic Geometry:

The electronic geometry around the central atom (carbon) is determined by the number of electron pairs around it. Carbon is bonded to two hydrogen atoms and two chlorine atoms, meaning it has four bonding pairs of electrons.

For four bonding pairs, the electronic geometry is tetrahedral.

6. Molecular Geometry:

Since there are no lone pairs on the central atom (carbon), the molecular geometry will also be tetrahedral.

7. VSEPR Structure:

Based on VSEPR theory, the structure is tetrahedral. The positions of the atoms are arranged symmetrically in a 3D space, with the two hydrogens and the two chlorines positioned around the carbon.

Conclusion:

Total valence electrons: 20
Lewis Structure: Shows carbon bonded to two hydrogen and two chlorine atoms with single bonds.
Formal charges: All atoms (C, H, Cl) have a formal charge of 0.
Resonance structures: None.
Electronic Geometry: Tetrahedral.
Molecular Geometry: Tetrahedral.
VSEPR structure: Tetrahedral arrangement around carbon.

This explains the structure and geometry of CH2Cl2 in a concise manner.