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BIOL 1F90 Lecture Notes - Fluorine, Sodium Bicarbonate, Hydrogen Fluoride

Biological Sciences
Course Code
Doug Bruce

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The Chemical Basis of Life I: Atoms,
Molecules, and Water
important to understand the behaviour of biological molecules
molecules are made of atoms (protons, neutrons, electrons)
atoms have no electric charge
Gold Foil Experiment:
Rutherford shot He nuclei (α particles) at a gold foil
α particles and nuclei both positively charged therefore when interacting they will
repel each other
98% went through the gold
<2% slightly deflected (passed close enough to nuclei to be effected)
0.01% bounced back
s are spherical
p are dumbell shaped
each orbital can hold only 2 electrons
atoms with more than 2 electrons has more than one orbital
more electrons = greater and greater distance from centre of nucleus
electrons vary in amount of energy
energy: the capacity to cause change
potential energy: electrons that are further away have more
energy that matter possesses because of its location and structure
electron's behaviour is driven by need to complete shells

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Nitrogen 7protons, 7electrons
2 electrons in the first shell
5 electrons in the second shell
2 in 2s orbitals
1 in each 3p orbitals
outer second shell isn't full
electrons in outer shell are available to combine: VALENCE ELECTRONS
Protons distinguish one element from another
Protons + Neutrons = atomic mass unit (amu)
Dalton: measurement of atomic mass
one dalton = 1/12 the mass of a carbon 12 atom
mole: Avogadro's number 6.022x1023
Isotopes: multiple forms of an element that differ in the number of neutrons
living organisms = 95% H, O, C, and N
H & O in water
N in proteins and nucleic acids
C is building blocks
mineral elements account for <1%
trace elements account for <0.01%
but are essential for growth
molecule: 2 or more atoms bonded together
organized in a specific fashion
compound: molecule composed of 2 or more elements
Types of Bonds:
covalent (polar, non-polar)
strong bond
can share 1, 2, or 3 electron pairs
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