The Name’s BOND……. Chemical Bond

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Cations/Anions What kind of atoms LOSE electrons and become positive? What kind of atoms GAIN electrons and become negative?

Diatomic Molecules Always exist in a chemical bond with another atom, even if the atom is of the same element H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

Chemical Bond Involves 2 atoms Mutual, electrical attraction between nuclei and valence electrons of 2 atoms

Chemical bonds: an attempt to fill electron shells 1.Ionic bonds – 2.Covalent bonds – 3.Metallic bonds

IONIC BOND bond formed between two ions by the transfer of electrons. ELECTRON STEALING !

Ionic Bonds: One Big Greedy Thief Dog!

Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to match the number of valence electrons of their nearest noble gas Positive ions form when the number of electrons are less than the number of protons Group 1 metals  ion 1+ Group 2 metals  ion 2+ Group 13 metals  ion 3+

Ions from Nonmetal Ions In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals Nonmetal add electrons to achieve the octet arrangement Nonmetal ionic charge: 3-, 2-, or 1-

Ionic Bonds Between atoms of metals and nonmetals with very different electronegativity –H–Huge difference in electronegativity –E–Electronegativity value > 1.7 Bond formed by transfer of electrons Produce charged ions all Form between elements located on opposite sides of the periodic table

Ionic Bonds (cont.) Conductors High melting point. Water soluble Crystallize (form crystals) Examples; NaCl, CaCl 2, K 2 O

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

COVALENT BOND bond formed by the sharing of electrons Electron sharing!

Covalent Bond Between nonmetallic elements of similar electronegativity. –Small electronegativity difference <1.7 Formed by sharing electron pairs, Formed between elements on the same side of the periodic table.

Covalent Bond (cont.) Stable non-ionizing particles Poor electrical conductors Brittle, nonmetals, low melting point Examples; O 2, CO 2, C 2 H 6, H 2 O,

Partial Charges Apply ONLY to COVALENT bonds Results when there is unequal sharing between 2 atoms Indicates electronegativity difference between bonded atoms

when electrons are shared equally, small electronegativity difference NONPOLAR COVALENT BONDS H 2 or Cl 2

when electrons are shared but shared unequally POLAR COVALENT BONDS H2OH2O

Polar Covalent Bonds--More One atom “keeps” electrons closer to it Electrons tend to reside around one atom more than the other atom Electrons still remain distributed between the 2 atoms--unequal

Polar Covalent Bonds: Unevenly matched, but willing to share.

Example: Cl 2, H 2 O

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

Multiple Covalent Bonds Single –1 bond between 2 atoms –2 electrons shared –Ex. H 2 Double –2 bonds between 2 atoms –4 electrons shared –Ex. O 2

Multiple Covalent Bonds (cont.) Triple –3 bonds between 2 atoms –6 electrons shared –Ex. N 2

Example: H 2 O, KI

Identify Bond type, Draw Lewis Structure to show bonding NaCl, CO

METALLIC BOND bond found in metals; holds metal atoms together very strongly

Electrons Localized: –Electrons hang out in a local area –Restricted to an atom/ion or shared between atoms Delocalized: –Electrons not attached to a particular area –Electrons are able to travel and move among atoms

Metallic Bonds Formed between atoms of metallic elements –Between atoms on left side of periodic table –Electronegativities are approximately equal Electron cloud around atoms, delocalized electrons –Valence electrons shared among multiple atoms, “neighbors” Electrons move through the whole metal, can jump between energy levels to create conduction bands.

Metallic Bonds (cont.) Delocalized electrons result in good electrical and thermal conductors 3-D network of metal ions and electron sea Examples; Na, Fe, Al, Au, Co

Metallic Bond, A Sea of Electrons

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Alloys Metallic compounds with 2 different elements Enhances metallic characteristics Ex. Sterling silver (approx %Ag, other metal—Cu) –Brass (Cu and Zn) –Stainless steel (contains chromium, prevents corrosion, structural component)

What is the point of chemical bonding? Physical/chemical properties vary based on –Structure –Bond type Ionic Bonds –High melting point –High boiling point Covalent Bonds –Lower melting point –Lower boiling point