CHEMISTRY The Building Blocks of Biology

Matter Anything that has mass and occupies space. Solid, Liquid, Gas

Elements

Biological Elements Nitrogen Carbon Hydrogen Oxygen Phosphorous Sulfur 96%

Elements Atom = smallest unit of matter unique to a particular element. –(smallest “piece” of an element) Molecule = union of 2 or more atoms. Compound = union of 2 or more different atoms.

Atomic Structure Determines how atoms act. Protons (+) Neutrons (no charge) Electrons (-) Atomic # Atomic Mass (Mass #) – an approximation. Nucleus Orbiting

Models of Atomic Structure Nucleus Cloud of negative charge (2 electrons) Electrons

Electron Shells 1 st Shell holds up to 2e - 2 nd Shell holds up to 8e - 3 rd Shell holds up to 8e -

Which element is this?

“Normally” # Protons = # Neutrons = # Electrons BUT, not always… Isotopes – Atoms with variable #’s of Neutrons –Stable & Unstable Ions – Atoms with variable #’s of Electrons

Atoms “like” to do 2 things: 1.Be Balanced. 2.Fill their outer-most shells.

“Valence” Electrons Those electrons occupying an atom’s outer-most shell (its “Valence Shell”)

Formation of Ions Oxidation – Departure of an e - Reduction – Gaining of an e - e-e-

Bonding Linking together atoms to form molecules… 1.Covalent Bonding 2.Ionic Bonding 3.Hydrogen Bonding 4.(Peptide Bonding)

Covalent Bonding Strong Sharing of valence electrons A.Non-Polar Covalent Bonds EQUAL SHARING H 2 O 2 H O

Covalent Bonding Strong Sharing of valence electrons B.Polar Covalent Bonds UNEQUAL SHARING H2OH2O O H H

Polar Covalent Bonds Water… This results in a partial negative charge on the oxygen and a partial positive charge on the hydrogens. H2OH2O –– O H H ++ ++ Because oxygen (O) is more electronegative than hydrogen (H), shared electrons are pulled more toward oxygen.

Ionic Bonding Electrons are transferred (not shared) –Oxidation forms a Cation (+ charged). –Reduction forms an Anion (- charged). Bond results from the attraction between ions of different charge…

Ionic Bonding Attraction between a Cation & an Anion. Cl – Chloride ion (an anion) – The lone valence electron of a sodium atom is transferred to join the 7 valence electrons of a chlorine atom. 1 Each resulting ion has a completed valence shell. An ionic bond can form between the oppositely charged ions. 2 Na Cl + Na Sodium atom (an uncharged atom) Cl Chlorine atom (an uncharged atom) Na + Sodium on (a cation) Sodium chloride (NaCl)

Hydrogen Bonding Weak A hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. + —

Hydrogen Bonding Water (H 2 O) Ammonia (NH 3 ) O H H  + +  – – N H H H A hydrogen bond results from the attraction between the partial positive charge on the hydrogen atom of water and the partial negative charge on the nitrogen atom of ammonia. ++ ++

Next…Water