Chemical Basis of Life Chapter 2&3

Chemical Basis of Life Chapter 2&3 - The Chemical Basis...

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Unformatted text preview: The Chemical Basis of Life Atoms to Molecules Chapter 2 & 3 Fig. 2.01 H 1 Chemical symbol HYDROGEN 1 AT. MASS 1.01 amu Na 11 SODIUM 2 • 8 • 1 AT. MASS 22.99 amu Mg 12 2 • 8 • 2 AT. MASS 24.31 amu MAGNESIUM C 6 2 • 4 AT. MASS 12.01 amu CARBON N 7 2 • 5 AT. MASS 14.01 amu NITROGEN O 8 2 • 6 AT. MASS 16.00 amu OXYGEN Ne 10 2 • 8 AT. MASS 20.18 amu NEON He Ne Ar Kr Xe Rn F Cl Br I At O S Se Te Po N P As Sb Bi C Si Ge Sn B Ai Ga In Zn Cd Cu Ag Ni Pd Pt Cl 17 2 • 8 • 7 AT. MASS 35.45 amu CHLORINE P 15 2 • 8 • 5 AT. MASS 30.97 amu PHOSPHORUS S 16 2 • 8 • 6 AT. MASS 32.07 amu SULFUR Ca 20 2 • 8 • 8 • 2 AT. MASS 40.08 amu CALCIUM K 19 2 • 8 • 8 • 1 AT. MASS 39.10 amu POTASSIUM Periodic Table Fe Ru Os Co Rh Ir Mn Tc Re Cr Mo W V Nb Ta Ti Zr Hf Sc Y (L) (A) Be Mg Ca Sr Ba H Li Na K Rb Cs Ra Fr Atomic number Chemical name Number of e – in each energy level (L) (A) La Ac Sm Pu Eu Am Gd Cm Tm Md Y N Bk Cf Es Fm After reviewing the Periodic Table of the Elements An atom is uniquely identified as an element by its number of A. Protons B. Neutrons C. Electron D. Neutrinos Fig. 2.02 Carbon- 12 ( 12C ) (6 p , 6 n ) 6 Carbon- 14 ( 14C ) (6 p , 8 n ) 6 _ + + + + + + _ _ _ + + + + + + Be able to draw the protons, neutrons and electrons of an atom of C-12 and C-14. Which of these atoms has a nucleus that is the more stable? Be able to draw the nuclear particles and electron orbits for the neutral atoms of • Nitrogen • Oxygen • Hydrogen • Sodium • Potassium • Chloride • Magnesium • Sulfur It is important to apply the following to each neutral atom. # electrons per shell = 2N 2 , N= #shell Electrons travel in pairs within orbits in the different shells. Each shell contains four different electron orbits corresponding to the dimensions in space. Thus, there is greater stability with 8 electrons per shell. This is the Rule of 8. Fig. 2.05 Oxygen (O) Oxygen (O) Molecular oxygen (O 2 ) (double bond is formed) or O O O O Hydrogen (H) Hydrogen (H) Molecular hydrogen (H 2 ) or (a) Single covalent bond formation (b) Double covalent bond formation O O + H—H H—H Covalent bonds between two atoms are created by the sharing of electron orbits. Double bonds with nearly double the strength is formed with two electrons shared. Fig. 2.06 Methane (CH 4 ) H H H H C The molecule of methane shares four equal strength covalent bonds. The nuclear attraction of the H atom and the C atom are very similar. The sharing of the electron is close to 50% between the C and H atoms. The makes a non-polar covalent bond and a non-polar molecule. C Fig. 2. 07 Hydrogen (H) Oxygen (O) Hydrogen (H) Formation of polar covalent bonds Oxygen part Partial negative charge at oxygen end of molecule Partial positive charge at hydrogen end of molecule + + Water molecule (H 2 O) Hydrogen parts However, in molecules such as water the covalent bonds do not equally share the electrons. The electrons remain in the Oxygen outer shell more than 95% of the time. This unequal distribution...
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This note was uploaded on 04/27/2008 for the course BIO 203 taught by Professor Stiles during the Fall '07 term at Samford.

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Chemical Basis of Life Chapter 2&3 - The Chemical Basis...

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