Chapter 3

Question 1

Electronegativity

Answer 1

The ability of an atom in a molecule to attract shared electrons to itself.

Question 2

Covalent bonds

Answer 2

• Atoms can form bonds is by sharing electrons -
  
  • electrostatus - nucleus electron attraction
• Shared electrons enhance stability becuase now atoms feel full shells
• and the resulting collection of atoms is called a molecule.

Question 3

What is bond energy?

Answer 3

• the energy required to break the bond.

Question 4

Relate bond length and strength to the number of electron pairs shared in a covalent bond

Question 5

Determine formal charge

Question 6

Name elements that don’t follow octet rule

Answer 6

• less than 8
  
  • H, He, B (like 6 e^-
• Expanded octet
  
  • P
  • S
  • I
  • Br
  • Noble gases Ar and down

Question 7

What is resonance?

Answer 7

average structure

Question 8

What is bond order

Answer 8

sing, double, triple

Question 9

Average Bond order

Answer 9

(1 + 1 + 2)/3 = 4/3 = 1 1/3

The last paid of electrons is delocalized across multiple atoms

Answer 10

Question 11

What is bonding ruled by? Coulombic force

Answer 11

Electrostatus…

• where E has units of joules, r is the distance between the ion centers in nanometers, and Q₁ and Q₂ are the numerical ion charges.
  
  • the negative sign indicates an attractive force. That is, the ion pair has lower energy than the separated ions.
• A bond will form if the energy of the aggregate is lower than that of the separated atoms.

Question 12

How does size chnage in isoelectronic ions?

Answer 12

For isoelectronic ions, size decreases as Z increases.

Question 13

Rules and formula to determine formal charge

Answer 13

1. Atoms in molecules try to achieve formal charges as close to zero as possible.
2. Any negative formal charges are expected to reside on the most electronegative atoms.

For one atom:

Electrons around one free atom - valence electrons assigned

(Valence electrons)_assigned = (number of lone pair electrons) + 1/2(number of shared electrons)

Question 14

Compare and contrast the bonding found in the H₂ (g) and HF(g) molecules with that found in NaF(s).

Answer 14

• In H₂ and HF, the bonding is covalent in nature, with an electron pair being shared between the atoms. In
  
  • H₂ , the two atoms are identical, so the sharing is equal
  • HF, the two atoms are different, with different electronegativities, so the sharing is unequal, and as a result, the bond is polar covalent.
• Both are in marked contrast to the situation in NaF:
  
  • NaF is an ionic compound—an electron has been completely transferred from sodium to fluorine—producing separate ions.

Question 15

Cation and parent atom

Answer 15

cation < parent

Question 16

Anion and parent atom

Answer 16

anion > parent atom