Chemistry Review

Review Concepts  Atom: smallest unit of matter that maintains ALL of the properties of an element  Proton, Neutron, Electron: (+), (0), (-)  Element: substance that cannot chemically be broken down any further  Compound: two or more elements combined  Matter: has mass and takes up space

The Specifics  Protons and Neutrons are located in the atomic nucleus together.  Electrons are found in the outer valence shells of the atom.  Atomic mass is measured in daltons: –1 proton/neutron = 1 dalton = 1 amu –Equal to g  Electrons are not counted as part of the atomic mass b/c they are 1/2000 of 1 amu.

In the HUMAN BODY  96% of the body is made up of 4 elements: –Carbon, Hydrogen, Oxygen, & Nitrogen  The remaining 4 percent is composed of several important elements: –P, Ca, K, S, Na, Cl, Mg –Several trace elements  concentration less than 0.01 %- Fe, Cu, F, I, Sn

Reading the Periodic Table 25 Mn Atomic number Atomic Weight Tells number of protons in the nucleus Mass in the nucleus

Isotopes  All atoms of the same element contain the same number of protons  **Some atoms have a greater number of neutrons and therefore have a greater atomic weight– these are isotopes**  Most common isotope = carbon –Carbon 12, Carbon 13, and Carbon 14 –All have 6 protons, but different number of neutrons

Orbitals  Orbitals are 3D spaces in which electrons are found  s, p, d, and f orbitals exist  No more than 2 electrons can be in the same orbital  1s and 2s orbital are both circular  2p orbital is dumbell shaped with X, Y, and Z plane

Remember:  The elements on the far right of the periodic table are generally “unreactive”.  Unpaired electrons are the reason for chemical reactions  Covalent bonds and Ionic bonds are the strongest chemical bonds.

Covalent Bonds  Occurs when electrons are shared between two or more elements  When 1 electron is shared a single covalent bond is formed  When 2 electrons are shared between elements a double covalent bond is formed.

Compounds and Molecules  Molecules are formed between 2 atoms of the same element  O2 or H2  Compounds are formed between two or more elements  H2O

Electronegativity  Defined as the attraction for a covalent bond  Non-polar covalent bonds are formed between elements that have the same electronegativity  Polar covalent bonds are formed when one atom in the bond has a higher electronegativity.

Ionic bonds  Typically form when an electron is pulled away from an element by another element  Cation- positive charged atom  Anion- negative charged atom  Ionic bonds are very dependent on the environment to form and stay together –Temperature, humidity, exposure to other elements

Weaker Interactions  Other bonds exist in chemical interaction  H bonds  Van der Waals forces  All very influential in biological chemistry  Influences shape, structure, and formation of specific molecules (proteins)

Hydroxyl Group  Hydrogen atom is bonded to an oxygen atom  Alcohols  Water molecules are attracted to the hydroxyl group because of polarity

Carbonyl Group  Carbon atom double bonded to the oxygen atoms with one hydrogen  Aldehyde: –Attached to a multiple carbon chain group  Ketone: –Attached to any other group

Carboxyl Group  Double bond of oxygen to carbon atoms that is then bonded to a hydroxyl group  When the –OH group disassociates it creates H + ions  This groups makes organic acids

Amino Group  Made of a nitrogen atom bonded to two hydrogen atoms and the carbon R group  Most common in biological systems as the ionized form = NH3 +  Combined with the carboxyl groups makes amino acids

Sulfhydryl Group  Made of sulfur atom bonding to a hydrogen atom  Resembles the OH group  Also involved with production of proteins

Phosphate Group  Carbon skeleton with an Oxygen atom at one end is bonded to a Phosphorus atom and 3 more oxygen atoms

Isomers  Isomers are molecules that have the same chemical formula but different arrangements of the atoms.  Structural isomers differ in terms of how atoms are joined together.  Optical isomers are mirror images of each other.  Optical isomers can occur whenever a carbon has four different atoms or groups attached to it.

Isomers