u3: lewis structure

Question 1

lewis bonding theory

Answer 1

• atoms are stable if they have a noble gas electron structure
• electrons are most stable when paired
• atoms form bonds to achieve stable octet
• stable octet achieved through electron transfer (metal+non-metal) or sharing (non-metals)

Question 2

where do leftover valence electrons go?

Answer 2

central atom

Question 3

which elements are exceptions to the octet rule?

Answer 3

• Be
• B
• P
• S
• Xe

Question 4

bond rules

Answer 4

• hydrogen and halogens (F, Cl, Br, I) form a single bond
• family oxygen (O, S, Se) forms 2 single bonds or 1 double bond
• family nitrogen (N, P, As) and boron forms 3 single bonds, 1 ingl bond+double bond, or a triple bond
• family carbon (C, Si) forms 4 single bonds, 2 double bonds, or…

Question 5

octet rule violation: Be

Answer 5

4

Question 6

octet rule violation: B

Answer 6

6

Question 7

octet rule violation: P

Answer 7

8 or 10

Question 8

octet rule violation: S

Answer 8

8, 10, or 12

Question 9

octet rule violation: Xe

Answer 9

8, 10, or 12

Question 10

coordinate covalent (dative) bond + example

Answer 10

• when one atom contributes a pair of electrons to form a bond
• NH4

Question 11

what can the central atom not be?

Answer 11

• usually not oxygen
• never hydrogen

Question 12

formal charge

Answer 12

calculated value used to compare number of valence electrons to number of electrons assigned to each atom in lewis structure

Question 13

what are formal charges used for?

Answer 13

to determine the best structure for an atom

Question 14

best lewis structure

Answer 14

• one with fewest charges
• puts negative charge on most electronegative atom

Question 15

lewis was doing his work at the same time as…

Answer 15

quantum mechanics was being developed

Question 16

what is the connection between bonding theory and atomic theory?

Answer 16

in lewis structure, the four sides around central atom correspond to the 4 orbitals (3s and 3p)

Question 17

what do lewis diagrams and orbital diagrams have in common?

Answer 17

they show the correct number of valence electrons

Question 18

resonance structure

Answer 18

group of lewis structures used to describe molecules that can be depicted w/ a single lewis structure

Question 19

what do resonance structures not do? what are they instead?

Answer 19

• don’t flip back and forth between possible structures
• actual molecules are a hybrid or average of resonance structures

Question 20

example of resonance structure

Answer 20

• ozone, O3
• benzene, C6H6