Types of Chemical Bonds Based on the Octet Rule and Electronegativity

Atoms become stable when their outer energy level is completely full. A full energy level consists of 8 electrons*. Atoms form molecules to achieve a stable octet. Review Octet Rule *Except for helium

Review electronegativity Electronegativity is the tendency to attract electrons to complete an atom’s outer energy level. Fluorine 1s 2 2s 2 2p 5 All elements in the Halogen group (group 7A or 17) need one electron to complete a stable octet. Chlorine 1s 2 2s 2 2p 6 3s 2 3p 5 Bromine 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 5

Review electronegativity All other elements’ electronegativity is relative to Fluorine’s, less than 4. Fluorine has the highest Electronegativity (4) of all the elements

IONIC BONDS: “ Opposites Attract” Sodium EN=0.9 Chlorine EN=3.0 Na  Cl METALNON-METAL The goal: stable octet (strong pull)(weak pull)

IONIC BONDS: Na + Cl  NaCl Sodium EN=0.9 Chlorine EN=3.0 Na now has a positive charge. Cl has a negative charge. Since opposites attract, these ions form an IONIC BOND.  Cl Na + _ An ionic bond is the resulting attraction between a cation and an anion after an electron is transferred from the metal to the non-metal.

IONIC BONDS: Crystal structure MOST OFTEN FORMED BY: Group 1 (alkali metals) with Group 7A or 17 (Halogens) Group 2 (alkaline earth metals) with Group 6A or 16. CAN ALSO OCCUR BETWEEN: Groups 1 or 2 and polyatomic ions NaCl, KI, LiF MgO, BaS H 2 SO 4, LiNO 3, MgPO 4, KOH

NONPOLAR COVALENT: “ Even sharing” Cl + Cl  Cl 2 Cl 7 valence electrons 1 space available Equal pulling = equal sharing Chlorine EN=3.0 EXAMPLES: Diatomic Molecule: made of two atoms, same element. Includes: H 2 O 2 N 2 and the Halogens – Cl 2 Br 2 F 2 I 2. Most Carbon compounds The goal: Stable Octet

POLAR COVALENT: “ uneven sharing” H 2 + O  2H 2 O Hydrogen EN=2.1 Oxygen EN=3.5 H·H· O Oxygen needs 2 electrons to form a stable octet. Hydrogen can either gain one or lose one to form a stable shell. They both pull, but Oxygen pulls harder.

POLAR COVALENT: Unequal Sharing H·H· O H·H· Kinetic energy (movement) brings these atoms together. H·H· H·H· O H2OH2O Oxygen EN=3.5 Hydrogen EN=2.1 POLAR COVALENT BONDS occur in organic compounds. Organic compounds consist primarily of carbon and hydrogen; may also include nitrogen, oxygen, halogens as well as phosphorus, silicon and sulfur.carbon hydrogennitrogenoxygenhalogensphosphorussiliconsulfur Oxygen side is slightly negative; Hydrogen ends are slightly positive.

POLAR COVALENT: Organic Compounds POLAR COVALENT BONDS occur in organic compounds. Organic compounds consist primarily of carbon hydrogen nitrogen oxygen halogens phosphorus silicon sulfursulfur.

Metallic bonding – “ Freely moving electrons” Outer electrons are shared among all the atoms in the solid. Each atom gives up its outer electrons and becomes slightly positively charged. Negatively charged electrons hold the metal atoms together. Freely moving electrons give the metal good thermal and electrical conductivity.

Probability of locating electrons Electrons can be detected by instruments sensitive to electricity. Electrons are found at specific distances from the nucleus.