CHAPTER 6 IONIC AND COVALENT BONDS

IONIC COMPOUNDS What happens to electrons? What is the electronegativity difference? What type of elements are involved?

IONIC COMPOUNDS What is the simplest unit of the compound called? How is strength of the bond measured?

COVALENT COMPOUNDS What happens to electrons? What is the electronegativity difference? What type of elements are involved?

COVALENT COMPOUNDS What is the simplest unit of the compound called? How is strength of the bond measured?

IONIC PROPERTIES COVALENT PROPERTIES Very strong bond and Intermolecular forces due to electrostatic attraction High melting point and boiling point When (l) or dissolved in water (aq) ionic compounds will conduct electricity Hard and brittle Form a crystal lattice with unique crystal shapes Weaker bonds/ e are shared Low melting and boiling point Soft (usually l or g) Non-conductors Low intermolecular forces ◦H-bonding, dipole- dipole in polar covalent ◦London dipersion forces in non-polar covalent.

ION FORMATION REVIEW

Why do ions form? Atoms become stable by gaining or losing VALENCE electrons to achieve a full outer ENERGY level. ◦Losing electrons produces a POSITIVE charge and the ion is called a CATION. ◦Gaining electrons produces a NEGATIVE charge and the ion is called an ANION. Normally, atoms will try to achieve a full octet and noble gas electron configuration to become stable.

Ex. Li loses 1 electron and forms Li + which has the same electron configuration as Helium. [He]1s 1  [He] Ex. S gains 2 electrons and forms S –2 which has the same configuration as Argon. [Ne] 3s 2 3p 4  [Ne]3s 2 3p 6  [Ar]

Exceptions to the octet rule: Hydrogen and He only need 2 (not 8) to be stable, since they only include an S orbital. TRANSITION METALS do not have to achieve noble gas configuration to become more stable. Ex. Fe can have charges of +2, +3, or +6

Energy level diagram: (see board) Lose the 2 electrons in the 4 s orbital: +2 Lose the 2 electrons in the 4s and 1 from 3d: +3 Lose the 6 electrons in the 3d: +6

Ions have different properties than the parent atom. ◦Recall, the size of the ion changes. ◦Cations are smaller than the parent atom. Anions are larger than the parent atom. ◦Ions are more stable than the parent atom. Ex. Once sodium loses an electron, it is no longer reactive when it becomes +1. We can eat Na + in NaCl, but we could never eat Na (s) – it explodes in water!!!

FORMATION of a CRYSTAL LATTICE

NAMING IONIC COMPOUNDS