Question

lewis dot structure practice
name:
pd.
date:
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, 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.

nh₃ # v electrons ____
o₂ # v electrons ____
h₂s # v electrons ____
n₂ # v electrons ____
pf₃ # v electrons ____
sio₂ # v electrons ____

Explanation:

Step1: Find valence electrons for NI₃

N (Group 15) has 5 valence electrons; each I (Group 17) has 7. Total: $5 + (3 \times 7) = 5 + 21 = 26$

Step2: Find valence electrons for O₂

Each O (Group 16) has 6 valence electrons. Total: $2 \times 6 = 12$

Step3: Find valence electrons for H₂S

Each H (Group 1) has 1; S (Group 16) has 6. Total: $(2 \times 1) + 6 = 2 + 6 = 8$

Step4: Find valence electrons for N₂

Each N (Group 15) has 5 valence electrons. Total: $2 \times 5 = 10$

Step5: Find valence electrons for PF₃

P (Group 15) has 5; each F (Group 17) has 7. Total: $5 + (3 \times 7) = 5 + 21 = 26$

Step6: Find valence electrons for SiO₂

Si (Group 14) has 4; each O (Group 16) has 6. Total: $4 + (2 \times 6) = 4 + 12 = 16$

Answer:

NI₃ # v electrons: 26
O₂ # v electrons: 12
H₂S # v electrons: 8
N₂ # v electrons: 10
PF₃ # v electrons: 26
SiO₂ # v electrons: 16