Chapter 2- the-chemical-foundation-of-life.pptx - BIOLOGY...

BIOLOGY 325: Inquiries in Biological Science
Chapter 2 Notes

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The Chemical
Foundation of Life
Atoms, Isotopes, Ions, and Molecules: The Building Blocks
Water
Carbon
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•
The Structure of the Atom
•
Atomic Number and Mass
•
Isotopes
•
The Periodic Table
•
Electron Shells and the Bohr Model
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Electron Orbitals
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Chemical Reactions and Molecules
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Ions and Ionic Bonds
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Covalent Bonds and Other Bonds and Interactions
Atoms, Isotopes, Ions, and Molecules: The Building Blocks
The Chemical Foundation of Life > Atoms, Isotopes, Ions, and Molecules: The Build...
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• An atom is composed of two regions: the nucleus, which is in the center of the
atom and contains protons and neutrons, and the outer region of the atom, which
holds its electrons in orbit around the nucleus.
•
Protons and neutrons have approximately the same mass, about 1.67 × 10-24
grams, which scientists define as one atomic mass unit (amu) or one Dalton.
• Each electron has a negative charge (-1) equal to the positive charge of a proton
(+1).
• Neutrons are uncharged particles found within the nucleus.
The Structure of the Atom
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Structure of an atom
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The Chemical Foundation of Life > Atoms, Isotopes, Ions, and Molecules: The Build...

• Atoms of each element contain an equal number of protons and electrons.
•
The number of protons determines an element's atomic number and is used to
distinguish one element from another.
•
The number of neutrons is variable, resulting in isotopes, which are different
forms of the same atom that vary only in the number of neutrons they possess.
•
Together, the number of protons and the number of neutrons determine an
element's mass number.
•
Since an element's isotopes have slightly different mass numbers, the atomic
mass is calculated by obtaining the mean of the mass numbers for its isotopes.
Atomic Number and Mass
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Atomic number, chemical symbol, and mass
number
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The Chemical Foundation of Life > Atoms, Isotopes, Ions, and Molecules: The Build...

• Isotopes are atoms of the same element that contain an identical number of
protons, but a different number of neutrons.