Question

ch₂o # v electrons ____
ch₂s # v electrons ____

ch₄ # v electrons ____
ch₃f # v electrons ____

ch₃oh # v electrons ____
c₂h₆ # v electrons ____

rules for drawing lewis dot structures:

1. count the total number of valence electrons in each atom and add them together to get the total number of electrons in the molecule. (for example, ccl₄ has 4 + (7×4) = 32 valence electrons.)
2. arrange atoms. place the atom that is farthest from fluorine on the periodic table, as the central atom. place the remaining atoms on the top, bottom, right and left sides. (h can never be a central atom)
3. put a bond between each surrounding atom and the central atom. each bond uses two valence electrons.
4. complete an octet (8) on one surrounding atom before proceeding to the next surrounding atom. once all surrounding atoms have octets, any remaining electrons should be placed on the central atom to achieve an octet. (h only makes one bond)
5. if there are not enough electrons to give the central atom an octet, make multiple bonds by moving electron pairs from surrounding atoms. (multiple bonds may occur with c, o, n, s, p)
6. double check the number of electrons and octets!! the number of electrons in the final structure must equal the number of valence electrons from step 1.

Explanation:

Step1: Valence electrons for CH₄O

C:4, H:1×4, O:6. Sum: $4 + (1×4) + 6 = 14$

Step2: Valence electrons for CH₃S

C:4, H:1×3, S:6. Sum: $4 + (1×3) + 6 = 13$

Step3: Valence electrons for CH₄

C:4, H:1×4. Sum: $4 + (1×4) = 8$

Step4: Valence electrons for CH₃F

C:4, H:1×3, F:7. Sum: $4 + (1×3) + 7 = 14$

Step5: Valence electrons for CH₃OH

C:4, H:1×4, O:6. Sum: $4 + (1×4) + 6 = 14$

Step6: Valence electrons for C₂H₆

C:4×2, H:1×6. Sum: $(4×2) + (1×6) = 14$

Answer:

CH₄O: 14
CH₃S: 13
CH₄: 8
CH₃F: 14
CH₃OH: 14
C₂H₆: 14