Electronegativity and Bond Types Quiz

Electronegativity and Bond Type

• Electronegativity is used to determine the type of bond formed between atoms.
• Electron affinity measures the tendency of an atom to accept an electron.
• Noble gases generally do not form compounds.

Electronegativity Values

• A table of electronegativity values for selected elements is provided.
  • Values range from 0.7 to 4.0
  • Metals, metalloids, and nonmetals are categorized.

Bond Character

• Differences in electronegativity determines the nature of the chemical bond.
• A difference greater than 1.7 indicates mostly ionic bond
• A difference of 0.4-1.7 indicates polar covalent bond
• A difference less 0.4 indicates nonpolar covalent bond

Polar Covalent Bonds

• Atoms unequally share electrons in a polar covalent bond .
• Electrons spend more time near one of the atoms.
• This creates a dipole moment (partial charges) on the ends of the molecule

Water and CCl4

• Water (H₂O) molecules are polar.
• Carbon tetrachloride (CCl₄) molecules are nonpolar because its shape creates a symmetrical distribution of charge.

Polar Covalent Bond Examples

• H-Cl: electronegativity difference =0.96. Thus, polar.
• H₂O: polar
• NH₃: polar
• CCl₄: Nonpolar

Properties of Covalent Compounds

• Covalent bonds between atoms are strong, but intermolecular forces are weak.

• Weak intermolecular forces result in relatively low melting and boiling points of molecular substances.

• Molecules can sometimes align in a crystal lattice similar to an ionic crystal lattice.

• Nonpolar molecules display a weak dispersion force (induced dipole)

• A hydrogen bond forms between a hydrogen end of one dipole and a fluorine, oxygen, or nitrogen on another dipole. This is an especially strong dipole-dipole force.

• Covalent network solids have only atoms that are interconnected by a network of covalent bonds.

• Quartz and diamonds are examples of materials classified as covalent network solids.