Chemistry of Life
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Element | A substance that cannot be broken down into simpler substances by chemical reactions.
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Atom | Smallest possible unit of an element that retains the physical and chemical properties of its element.
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Subatomic Particles | (Neutron= No charge) (Proton= +1 Charge) (Electron= -1 Charge)(Proton & Neutron found in the nucleus, masses about the same) (Electron orbits around nucleus held by electrostatic attractions of positively charged nucleus. Mass extremely small)
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Atomic Number | Number of protons in an atom. Every atom has equal number of protons and electrons. No electric charge. All atoms of an element have the same atomic number.
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Atomic Mass | Number of protons and neutrons in an atom. Mass of the whole atom. Unit= AMU. • Number of neutrons can vary in an element, but number of protons is constant.
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Isotopes | Atoms of an element that have the same atomic number but different mass number. Same # of protons, but different # of neutrons. • Different isotopes of the same element react chemically in same way. Some isotopes are radioactive.
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The energy levels of electrons | Light negatively charged particles that orbit around nucleus.
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First energy level: | Has one spherical s orbital (ls orbital)
Holds a maximum of two electrons.
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Second energy level: | Holds a maximum of eight electrons
One spherical s orbital (2s orbital)
Three dumbbell-shaped orbitals each oriented at right angles to the other two (2px, 2py, 2pz orbitals
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Third energy level: | Contain s and p orbitals
Contain additional orbitals with more complex shapes
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An atom with a complete valence shell is unreactive or inert | An atom with an incomplete valence shell is chemically reactive (tends to form chemical bonds until it has eight electrons to fill the valence shell).
Atoms with the same number of valence electrons show similar chemical behavior.
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Atoms combine by chemical bonding to form molecules |
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Type of Chemical Bonds | Single covalent bonds' atoms may freely rotate around the axis of the bond. Double and Triple convalent bonds are rigid and do not allow rotation.
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pH scale and its use. | Occasionally, the hydrogen atom that is shared in a hydrogen bond between two water molecules, shifts from the oxygen atom to the unshared orbitals of the oxygen atom.
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Organisms are sensitive to changes in pH | 1. Acids and bases
Note that brackets indicate molar concentration.
NOTE: only 1 out of 554,000,000 water molecules are actually dissociated.
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The pH scale | In any aqueous solution
[H+][OH-] = 1.0 x 10-14
For example:
In a neutral solution, [H+] = 10-7 M and [OH-] = 10-7 M.
In an acidic solution where the [H+] = 10-5 M, the [OH-] = 10-9 M.
In a basic solution where the [H+] = 10-9 M, the [OH-] = 10-5 M.
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PH SCALE | pH of 7 is a neutral solution.
pH < 7 is an acidic solution.
pH > 7 is a basic solution.
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Buffers | By minimizing wide fluctuations in pH, buffers help organisms maintain the pH of body fluids within the narrow range necessary for life (usually pH 6-8).
Buffer = Substance that minimizes large sudden changes in pH.
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judton1
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