Using the "octet rule" write the Lewis formulas for NF3 and NO3-.
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To write the Lewis formulas for NF3 and NO3-, we need to follow the "octet rule." The octet rule states that atoms tend to gain, lose, or share electrons in order to have a full set of eight valence electrons.
First, let's start with NF3:
1. Determine the total number of valence electrons: Nitrogen (N) has five valence electrons, and Fluorine (F) has seven valence electrons. Since we have three fluorine atoms, the total number of valence electrons is 5 + (3 × 7) = 26.
2. Place the least electronegative atom in the center: Nitrogen is less electronegative than fluorine, so it will be placed in the center.
3. Connect the outer atoms to the central atom with single bonds: Place one fluorine atom on each side of the nitrogen atom, forming three single bonds between them.
4. Distribute the remaining electrons to satisfy the octet rule: After forming the three single bonds, we have used six electrons (2 from each bond). We have 26 - 6 = 20 valence electrons left. Place the remaining electrons around the fluorine atoms, giving each fluorine a total of eight electrons around it.
This results in the Lewis formula for NF3:
F N F
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F
Now, let's move on to NO3-:
1. Determine the total number of valence electrons: Nitrogen (N) has five valence electrons, and Oxygen (O) has six valence electrons. Since we have three oxygen atoms, the total number of valence electrons is 5 + (3 × 6) + 1 (for the negative charge) = 24.
2. Place the least electronegative atom in the center: Nitrogen is less electronegative than oxygen, so it will be placed in the center.
3. Connect the outer atoms to the central atom with single bonds: Place one oxygen atom on each side of the nitrogen atom, forming three single bonds between them.
4. Distribute the remaining electrons to satisfy the octet rule: After forming the three single bonds, we have used six electrons (2 from each bond). We have 24 - 6 = 18 valence electrons left. Place all the remaining electrons around the oxygen atoms, giving them each a total of eight electrons.
However, the NO3- ion carries an extra negative charge, which means it has one additional electron. Therefore, we add one more electron to the Lewis structure.
This results in the Lewis formula for NO3-:
O
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O--N--O
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O-