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Lecture 2

BIOL 2160 Lecture Notes - Lecture 2: Amine, Covalent Bond, Carboxylic Acid

Biological Sciences
Course Code
BIOL 2160
Cross- Eyed

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An understanding of chemistry is important because the interaction between atoms is one
of the lowest levels of biological organization.
The basic unit of all forms of matter: atom
o Smallest unit of matter that retains the physical and chemical properties of the
o Made up of 3 subatomic particles.
o The 3 most stable subatomic particles are: neutrons (nucleus), protons (nucleus),
and electrons (around nucleus).
Constantly in motion.
All have positive charge, but do not have the same amount of positive
charge. (for nucleus)
The electron orbitals: the three-dimensional space around the nucleus of an atom where
an electron will be found.
o Most elements are trying to get full outside electron shell (8 electrons)
Exception of hydrogen and helium because they only need two.
The chemical behavior of an atom is determined by the number of electrons in the
outermost electron shell.
An atom with an incomplete (partially full) electron shell is reactive whereas an atom
with a full electron shell is inert, or not chemically active.
Combustion: reaction with oxygen.
o The Hindenburg (1937): exploded blimp due to combustion.
o Blimps today have helium because its outer shell is full, making it un-explosive.
o Nobel gases are not explosive.
If an atom has a vacancy in the outer electron shell, it will try to fill that vacancy or get
rid of the “extra” electrons so the outer shell is full.
o A reactive atom will try to fill the valence shell by interacting with other atoms.
o This interaction may result in two atoms forming a chemical bond.
If one atom gets filled but another doesn’t, than the bond doesn’t
happen… both need to be unstable.
o Move towards path of least resistance.
o Same number of protons and electrons no charge.
A chemical bond is an attraction that holds two atoms together.
A molecule is two or more atoms held together by chemical bonds.
Atom: smallest unit that retains the physical and chemical properties of a
If an atom has an almost empty or an almost full outer electron shell is likely to form an
o An ion is a charged atom or molecule. It is charged because it has either lost or
gained electrons.
All thing son periodic table are neutral until gain/loss atoms.
Not all atoms are likely to become ions.
Atoms that are most likely have an almost completely full or
completely empty shell.
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Gaining or losing electrons doesn’t require as much effort for these
o An anion is a negatively charged atom or molecule because it has gained an
o A cation is a positively charged atom or molecule because it has lost an electron.
o Opposite charges attract (think of bond between +Sodium and Chlorine)
Covalent bond: a bond formed when two atoms share pairs of electrons.
o Space around atom is community space; doesn’t belong to atom.
Nonpolar covalent bond: is a covalent bond in which sharing of the electron pair is
o Nonpolar means equal.
o H2 is nonpolar; no charge on either atom
Polar covalent bond: a covalent bond in which the sharing of the electron pair is
o Polar means opposite or extreme; sharing is unequal.
o Water molecule is one of the most polar things that exists.
Atoms are more attracted to nucleus of oxygen than hydrogen because
they are closer to hydrogen.
Water molecule is charged; has positive and negative end.
Electronegativity: defined as an atom’s ability to attract and hold electrons. An
indication of how much positive charge is in the nucleus. Assigned a numerical value.
The higher the #, the more electronegative.
o H C N O } must know; make up 96% of body are made of these.
If the atoms in a bond are right next to each other on the list above:
If the atoms are separated by at least one: POLAR
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