Bonding

Essential Question Why do some elements bond with some, but not others? Assessment: Lab report

The octet rule Elements become stable by achieving same configuration of valence electrons as one of the noble gases (noble gas configuration) When atoms collide, outer electrons rearrange to achieve stable octet of valence electrons How do they rearrange? 1. Transfer valence electrons between atoms 2. Share valence electrons between atoms

Ionic bond Ion = atom that has a charge because of loss or gain of electrons Electrons transferred from one atom to another

Ionic bond Electrons transferred from one atom to another

Bonding patterns Ionic bond Covalent bond Electrons transferred Electrons shared Between atoms that have different electronegativity (high and low) Between atoms that have high electronegativity Metals and non metals Non metals and non metals

Electronegativity Measure of the ability of an atom in a chemical compound to attract electrons The atom with higher electronegativity will pull on the electrons more strongly that other atoms will

Ionic bond Oxidation number = charge on an atom Switcheroo!

Ionic bond Short quiz on ionic bonding next class. Know: Ionic vs covalent Charges of different elements on the periodic table How to form compounds How to name compounds Resources: Ionic bonding notes & puzzle activity

Lewis Dot Diagram Illustrates valence electrons as dots around the chemical symbol of an atom.

Covalent bond Electrons shared between atoms Hydrogen requires one more e- to have same configuration as helium Oxygen requires two more e- to have the same configuration as neon

Covalent bond

Covalent bonds More than two electrons can be shared

Classes of Elements Metals – elements that have luster, conduct heat and electricity (e.g. copper jewelry, polished silverware) Nonmetals – most are gas at room temp, do not conduct electricity, poor conductor of heat than metals (e.g. oil – carbon rich) Metalloids – semiconductor (does not conduct electricity as well as metal but conducts better than nonmetal) (e.g. silicon in microchips of electronics)

Bonding patterns Ionic bond Covalent bond Solids at room temperature Can be solid, liquids or gases at room temperature Higher melting point than covalent compound – why? Low melting point than ionic compounds Conduct electric current – why? Do not conduct electric current