LECTURE 6.2LECTURE 6.2

BONDING AND THE PERIODIC BONDING AND THE PERIODIC TABLETABLE

Ionic BondingIonic BondingCovalent BondingCovalent BondingMetallic BondingMetallic BondingVan der Waals BondingVan der Waals BondingHydrogen BondingHydrogen Bonding

THE THREE PRIMARY OR THE THREE PRIMARY OR STRONG BONDSSTRONG BONDS

Metal to Non-Metal: Ionic (Chapter 15)Metal to Non-Metal: Ionic (Chapter 15)Non-Metal to Non-Metal: Covalent Non-Metal to Non-Metal: Covalent

(Chapter 16)(Chapter 16)Metal to Metal: Metallic (Chapter 17)Metal to Metal: Metallic (Chapter 17)

THE SECONDARY OR WEAK THE SECONDARY OR WEAK BONDSBONDS

Hydrogen: Between “Electropositive” and Hydrogen: Between “Electropositive” and “Electronegative” Elements. Permanent “Electronegative” Elements. Permanent Dipoles (Chapter 19) Dipoles (Chapter 19)

WATER!WATER!van der Waals: Fluctuating Dipoles van der Waals: Fluctuating Dipoles

(Chapter 18)(Chapter 18)NOBLE GASESNOBLE GASES

THE IONIC BONDTHE IONIC BOND

The establishment of the "Noble gas The establishment of the "Noble gas configuration" by electron transfer from configuration" by electron transfer from metallic atoms to non-metallic atoms. The metallic atoms to non-metallic atoms. The electrostatic bond is thus formed between electrostatic bond is thus formed between positively charged metallic ions (cations), positively charged metallic ions (cations), and negatively charged ions (anions). and negatively charged ions (anions).

Ionic bonds are Ionic bonds are non-directional.non-directional.

THE IONIC BONDTHE IONIC BOND

Always produces Always produces compoundscompounds. Examples include . Examples include NaCl (common salt), NaNaCl (common salt), Na22O (natron) and O (natron) and

magnesium oxide (MgO), where one species is magnesium oxide (MgO), where one species is metallic (the cation) and is from groups I-III or metallic (the cation) and is from groups I-III or the transition metals: the other species is non-the transition metals: the other species is non-metallic (the anion),metallic (the anion),** and is from Groups V, VI or and is from Groups V, VI or VII. Most importantly, ionically bonded solids are VII. Most importantly, ionically bonded solids are non-metallic and inorganic – they are ceramics.non-metallic and inorganic – they are ceramics. * A Negative ION.* A Negative ION.

THE IONIC BONDTHE IONIC BOND

Ionic Bond: arises from the electrostatic attraction between cations and anions. Because the cations are everywhere positive, and the anions are everywhere negative, the bond is non-directional.

a

+_

THE COVALENT BONDTHE COVALENT BOND

The attainment of the "magical octet" of The attainment of the "magical octet" of outer shell electrons by atoms sharing outer shell electrons by atoms sharing pairs of valence electrons. pairs of valence electrons.

Each shared electron pair constitutes a Each shared electron pair constitutes a single bond. single bond.

Covalent bonds are Covalent bonds are directional.directional.

THE COVALENT BONDTHE COVALENT BOND

Occurs in non-metallic (Groups IV, V, VI Occurs in non-metallic (Groups IV, V, VI and VII) elements to form e.g., network and VII) elements to form e.g., network solids (diamond carbon and silicon) and solids (diamond carbon and silicon) and molecular gases (hydrogen, oxygen). molecular gases (hydrogen, oxygen).

Covalent bonding also occurs in Covalent bonding also occurs in compounds, as in the network solids SiC compounds, as in the network solids SiC (both Group IV elements), and SiO(both Group IV elements), and SiO22 (Groups IV and VI respectively) and (Groups IV and VI respectively) and molecular gases (e.g., carbon dioxide).molecular gases (e.g., carbon dioxide).

COVALENT BONDCOVALENT BOND

Covalent Bond: arises from the electrostatic attraction between cations/cation cores and shared electron pairs. The electrons are said to be localized, because they are confined, primarily between adjacent cationsHence, the covalent bond is directional.

a

+ +_

THE METALLIC BONDTHE METALLIC BOND

The bonds formed between an array of positively The bonds formed between an array of positively charged metallic cations and a "sea" of charged metallic cations and a "sea" of negatively charged, free-electrons, the latter negatively charged, free-electrons, the latter being "donated" from the outer shells of the being "donated" from the outer shells of the constituent atoms. constituent atoms.

Metallic bonds are Metallic bonds are non-directional.non-directional. Occurs for all metallic elements and their alloys Occurs for all metallic elements and their alloys

(i.e., Group I, I and III metals and for the (i.e., Group I, I and III metals and for the transition metals), to form close-packed solidstransition metals), to form close-packed solids

METALLIC BONDMETALLIC BOND

Metallic Bond: arises from the electrostatic attraction between cation cores and an electron cloud. The electrons are said to be delocalized, because they are not confined, to any cation core, but are “free” to move between the cation cores.Hence, the metallic bond is non-directional.

a

+ +_

RUTHERFORD-BOHR MODELSRUTHERFORD-BOHR MODELS

IONIC BONDING IN MAGNESIUM OXIDEIONIC BONDING IN MAGNESIUM OXIDE

THE CRYSTAL STRUCTURE OF THE CRYSTAL STRUCTURE OF MATGNESIUM OXIDEMATGNESIUM OXIDE

AN IONIC COMPOUND; AB2AN IONIC COMPOUND; AB2

HYDROGEN: THE SIMPLEST HYDROGEN: THE SIMPLEST MOLECULEMOLECULE

THE METHANE MOLECULE, PARAFFINS THE METHANE MOLECULE, PARAFFINS AND MOLECULAR WEIGHTAND MOLECULAR WEIGHT

ELECTRON-DOT REPRESENTATIONS OF ELECTRON-DOT REPRESENTATIONS OF COVALENTLY-BONDED ELEMENTSCOVALENTLY-BONDED ELEMENTS

STRUCTURE OF COVALENTLY BONDED STRUCTURE OF COVALENTLY BONDED ELEMENTSELEMENTS

THE MONOMER AND TETRAMER OF THE MONOMER AND TETRAMER OF DIAMOND-CARBONDIAMOND-CARBON

THE MONOMER AND CRYSTAL THE MONOMER AND CRYSTAL STRUCTURE OF DIAMONDSTRUCTURE OF DIAMOND

THE “HARD-SPHERE” AND “BALL AND THE “HARD-SPHERE” AND “BALL AND STICK” MODELS OF DIAMOND-CARBONSTICK” MODELS OF DIAMOND-CARBON

COVALENTLY BONDED COVALENTLY BONDED NETWORK SOLIDNETWORK SOLID