Draw a complete Lewis Structure (showing all bonds and lone pairs) for a molecule with the general formula AX4, if A was from group 4A and X was from group 7A
Drawing lewis structures
1. Calculate Valence Number (total #valence electrons - from group number)
2. Calculate Octet Number (total #electrons after bonding - always 8 (nonmetals) except for hydrogen and complex substrates => 2)
3. Calculate Bond Number (#Cov. Bonds = (V - O)/2 )
1. Valence# = 1A + 4X = 1(4) + 4(7) = 32 (sum is always even no.; complex substrates => Valence = 1 => like a methyl group or iso-propyl group; elements (non-metals)
2. Octet# = 1A + 4X = 1(8) + 4(8)= 40 (all nonmetal elements have octet (8) except for hydrogen and complex substrates = 2)
3. Bond# = (V#-O#)/2 =(40-32)/2 = 8/2 = 4 Cov Bonds
DRAW STRUCTURE => A is central element, X substrates.
X
!
X-A-X
!
X
The !-X is supposed to be over and under the A.
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To draw a Lewis structure for a molecule with the general formula AX4, where A is from group 4A (or Group 14) and X is from group 7A (or Group 17), we need to follow a set of steps.
Step 1: Determine the total number of valence electrons.
In this case, A represents an element from group 4A (such as Carbon (C) or Silicon (Si)), which has 4 valence electrons. X represents an element from group 7A (such as Chlorine (Cl) or Fluorine (F)), which has 7 valence electrons.
Since we have four X atoms, we will multiply the number of valence electrons of X by four.
So, Total number of valence electrons = (Number of valence electrons of A) + (Number of valence electrons of X) × 4
Total number of valence electrons = 4 + (7 × 4) = 4 + 28 = 32
Step 2: Determine the central atom.
In this case, the central atom (A) is from Group 4A. Generally, we use the least electronegative atom as the central atom. Thus, we can choose Carbon (C) as our central atom.
Step 3: Connect all the atoms using single bonds.
Place the central atom (C) in the center and surround it with four X atoms (Cl, for example), placing one bond between each atom. Remember, Carbon (C) forms four bonds.
Step 4: Place the remaining electrons as lone pairs.
Distribute the remaining valence electrons around the atoms to satisfy the octet rule (except for Hydrogen (H) which can only accommodate a maximum of 2 electrons).
Start by filling octets around the X atoms. Each X atom requires one electron to complete its octet, so place two electrons (as a lone pair) around each X atom.
Place the remaining valence electrons around the central atom (C) to complete its octet. In this case, you would place four lone pairs around Carbon (C).
At this point, you should have used all 32 valence electrons.
Step 5: Check if all atoms have an octet.
Ensure that each atom (except Hydrogen, which only needs 2 electrons) has a complete octet (8 valence electrons), including all atoms' lone pairs.
Step 6: Check the formal charges.
Calculate the formal charges on each atom to verify if they are all zero (or as close to zero as possible). Remember, formal charge can be calculated by subtracting the number of lone pairs and half the number of bonded electrons from the atom's valence electrons.
If the formal charges do not add up to zero, you may need to rearrange the electrons to minimize the formal charges. However, in this case, the Lewis structure should already have formal charges of zero on each atom.
Here is an example of the Lewis structure for AX4, where A is from group 4A and X is from group 7A, using Carbon (C) as the central atom and Chlorine (Cl) as the outer atoms:
Cl
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Cl –C– Cl
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Cl
I hope this helps! Let me know if you have any more questions.