Chemical Bonding

Chemical Bond The forces that hold groups of atoms together and make them function as a unit Bonding involves only the valence electrons Electrons are transferred or shared to give each atom a noble gas configuration (stable octet) ▫This is known as the octet rule 3 types of bonds: 1.Ionic Bond 2.Polar covalent 3.Covalent

Types of Bonds: Ionic Bond that is formed by a transfer of electrons from a metal to a non-metal. Ex: NaCl, LiNO 3 The compound is held together by electrostatic forces. Positive ion (cation) and negative ion (anion)

Types of Bonds: COVALENT TOTALLY equal sharing of electrons; Ex: Cl 2, O 2, N 2 Neither atom wants to give its valence electron because they both equally want an electron; their EA is equal to one another

Types of Bonds: POLAR COVALENT Unequal sharing of electrons; two non-identical non- metals. Ex: HCl and H 2 O The atom with the greater EN value will be able to pull and hold the pair of electrons closer it ▫Higher EN is “slightly negative” δ - ▫Lower EN is “slightly positive” δ + This unequal sharing of electrons is what makes a bond polar!

Terms Polar: having two poles (ends) where one is negatively charged, and the other is positively charged Dipole: an end of a molecule that has a charge

Context We know that atoms may share or take/give electrons to form 3 types of bonds: 1.Ionic Bond 2.Polar covalent 3.Covalent We can use the electronegativity values to determine how the electrons are moved/shared

BOND CONTINUUM RANGE An EN difference of GREATER than 1.7 is said to be ionic An EN difference LESS THAN 1.7 and GREATER than 0.5 is said to be polar covalent An EN difference of 0 – 0.49 is said to be covalent (non-polar) Electronegativity Difference 0 to 0.49 Nonpolar Covalent 0.5 to 1.69 Polar Covalent > 1.7 Ionic

Physical PropertyIonicCovalent State of matter at room temp. Solid Solid, liquid or gas Properties of Compounds

Physical Properties PropertyIonicCovalent Structure Hard Crystal Lattice: r epeating structure of anions and cations Soft

Physical PropertyIonicCovalent Melting point high low Ex. 801 o C for NaCl Ex. 80 o C for C 10 H 8

Physical PropertyIonicCovalent Solubility Soluble in water « like dissolves like » -Polar covalent compounds are soluble in water -Non-polar covalent compounds are soluble in non-polar solutions Molecular polarity of water helps to explain its ability to dissolve ionic compounds. The slightly negative end of water molecules are attracted to positive ions in an ionic crystal.

Physical PropertyIonicCovalent Conductivity electrolytenonelectrolyte

Physical Properties of Ionic and Covalent(molecules) Physical Property IonicCovalent State of matter SolidSolid, liquid or gas StructureHard Crystal Lattice Soft Melting pointHighLow SolubilitySoluble in waterLike dissolves like ConductivityElectrolyte in solution (ions present) Non-electrolyte (no ions present)

Polar Molecules Note: Not all molecules with polar bonds are polar molecules Polar molecules must have: 1.Polar bonds 2.Non-symmetrical shape of the molecule

Homework! Pg. 74 # 1, 2, 5, 6 P. 94 # 1-3