Chapter 8- Basic Concepts of Chemical Bonding

What is the Octet rule?

Atoms tend to gain, lose or share electrons until they are surrounded by eight valance electrons

What are the three types of chemical bonds?

• Ionic- electrostatic attraction between ions

• Covalent- sharing of electrons

• Metallic- metal atoms bonded to several other atoms

What occurs during ionic bonding?

• Metals tend to lose electrons

• Non-metals tend to gain electrons

What is lattice energy?

• The energy required to completely separate a mole of a solid ionic compound into its gaseous ions

• Increases with ionic charge

What occurs during covalent bonding?

• Atoms share electrons

• Attractions between electrons/nuclei and repulsions between electrons/nuclei

• Attractions must be greater than repulsion for bonds to form

Lewis Structures

• Try to give each atom the same number of electrons as the nearest noble gas by sharing electrons

• Lone pairs- electrons located on only one atom

• Bonding pairs- shared electrons

What is electronegativity?

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

• Increases as you go right across a period

What is the relationship between electronegativity and polar covalent bonds?

• When two atoms share electrons unequally

• The greater the difference in electronegativity, the more polar the bond

What is a dipole moment?

• Produced by two equal but opposite charges separated by a distance

• Measured in debyes (D)

Guide for Ionic vs Covalent Compounds

• Metal + nonmetal = ionic

• nonmetal + nonmetal = covalent

• lower melting points = covalent

What is a formal charge?

The charge an atom would have if all of the electrons in a covalent bond were shared equally

What are the exceptions to the octet rule?

• Ions/molecules with an odd number of electrons

• Ions/molecules with less than an octet

• Ions/molecules with more than 8 valence electrons

What is bond enthalpy?

How much energy is required to break a bond