Unit 6 Chemical Bonding Polar Bears and Penguins

What is a bond? Chemical Bond = link between atoms that results from mutual attraction of their nuclei for electrons.

Why do atoms form bonds? Atoms form bonds to achieve stability through lower potential energy

Why do atoms form bonds? Noble gases are stable bc full outer NRG level of electrons Most atoms need 8 valence electrons in their outer NRG level = Octet Rule

Electronegativity in the Periodic Table

3 Bonding Types The difference in electronegativity is what determines the bond type.

3 Types of Bonds Nonpolar Covalent = 2 identical atoms sharing electrons evenly (equal electronegativities) Polar Covalent = 2 nonmetal atoms that are different sharing electrons unevenly (unequal electronegativities) Ionic = A metal and a nonmetal in which electrons are taken (extreme difference in electronegativities)

Ionic Bond “My name is Bond. Ionic Bond. Taken not Shared.” Ionic = an attraction between positive ions (cations) and negative ions (anions)

Ionic Bond Cation: A positively charged ion – Formed from an atom that has LOST electrons (metal) Anion: A negatively charged ion – Formed from an that has GAINED electrons (nonmetal)

Dipole A dipole is a slight charge in a covalent bond An atom that attracts the electron more strongly creates a negative dipole.

Dipole

“Polar” Uneven pull of electrons Could be referring to an ionic bond, a covalent bond, or the entire molecule.

Polar vs Nonpolar Molecule

Covalent Bonding Electrons are shared Single bond= 2 electrons shared Double bond = 4 electrons shared Triple bond = 6 electrons shared Lone Pair = 2 electrons that are not bonded

Properties of Ionic Bonds Metal and nonmetal Usually crystalline solids High Melting Points Dissolves in water Does NOT dissolve in hexane May dissolve in isopropanol Conducts electricity

Properties of Nonpolar Covalent Bonds Formed between 2 or more nonmetals liquids or gases Have low melting points Do NOT dissolve in water Dissolves in hexane May dissolve in isopropanol Does not conduct electricity

Properties of Polar Covalent Bonds Formed between 2 or more nonmetals Soft solids Have low melting points May dissolve in water May dissolve in hexane May dissolve in isopropanol Usually does not conduct electricity