Chemical Basis of Life

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Chapter 2

• Chemical Basis of Life

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I. Elements Matter

• Matter
• - Matter refers to anything that has mass and
  takes up space.
• - Atoms are the smallest particles of matter.

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Elements and Atoms

• B. Elements
• 1. All matter is composed of elements
• 2. Elements are the basic substances that make
  up matter
• 3. Atoms are the smallest particles of matter
• 4. Living Organisms require about twenty
  elements
• 95 of human body is made of oxygen, carbon,
  hydrogen, and nitrogen

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Carbon, hydrogen, oxygen, and nitrogen Make up
the bulk of living matter
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Table 2.1
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• 5. Trace elements are common additives to food
  and water
• Dietary deficiencies in trace elements can cause
  various physiological conditions

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Figure 2.2B
Figure 2.2A
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C. Atomic Structure

• 1. Protons ()
• 2. Neutrons (neutral)
• 3. Electrons (-)

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• 4. Electron arrangement determines the chemical
  properties of an atom
• 5. Are arranged in shells, which may contain
  different numbers of electrons
• 1st- 2 electrons 2nd- 8 electrons
• 3rd- 18 electrons 4th- 32 electrons

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Drawing Bohr Models of Atoms
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D. Periodic Table of Elements
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Periodic Table of Elements
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How many protons, neutrons, and electrons?

• Step 1
• Use your periodic table to find and element.
• Step 2
• The number of protons ( charge)
• The atomic number 36
• Kr has 36 protons

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• Step 3
• The number of electrons (- charge)
• Remember atoms have no overall charge
• Atoms must have an equal number of protons and
  electrons
• Number of protons number of electrons
• Kr has 36 electrons

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• Step 4
• The number of neutrons (neutral/no charge)
• Mass number (atomic weight rounded to the nearest
  whole number)
• Neutrons mass number protons
• Kr neutrons 84 36 48

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• Summary
• Number of protons atomic number
• Number of electrons protons
• Number of neutrons
• mass number protons

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• Problems
• Find the protons (p), electrons (e-), and
  neutrons (n) of Oxygen.

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• Problems
• Find the p, e-, n of Xenon (Xe).

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• Problems
• Find the p, e-, and n of Zirconium (Zr).

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E. Atom Rules

• of Protons Atomic number
• of Protons of Electrons
• Mass Protons Neutrons

Symbol Atomic Mass p n e-
U 92 192
Na 11 23
Mg 24
Cu 65
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F. Isotopes

• 1. Isotopes have a different number of neutrons
  but the same number of protons
• 2. Radio active isotopes are used to detect
  problems with the thyroid, treat cancer, and
  detect problem with digestion

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• Isotopes

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Table 2.4
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G. Molecules and Compounds

• 1. Molecule when two or more atoms combine
  (usually for nonmetals)
• 2. Compound when two or more atoms of different
  elements combine
• Two types
• Ionic
• Covalent

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• 3. Elements can combine to form compounds

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II. Bonding

• A. Atoms whose shells are not full, tend to
  interact with other atoms and gain, lose, or
  share electrons. These interactions form chemical
  bonds

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B. Types of Bonding

• 1. Ionic
• A metal and non metal
• Form ions
• Na
• O2-
• Transfer of electrons
• Ionic compounds
• Ions are important muscle contraction, nerve
  impulse transmission, etc.

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• Ionic bonds are attractions between ions of
  opposite charge

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Figure 2.7A
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• 2. Covalent
• 2 or more non metals
• Sharing of electrons forms a bond.
• Single double or triple
• Molecules formed when two or more atoms combine

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• C. Unequal electron sharing creates polar
  molecules
• A molecule is nonpolar
• When its covalently bonded atoms share electrons
  equally

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• In a polar covalent bond
• Electrons are shared unequally between atoms,
  creating a polar molecule

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• C. Hydrogen Bond
• Occurs when an atom of hydrogen has a strong
  attraction to two atoms instead of one
• The atoms must be highly electronegative
  (electron loving) like Oxygen, Flourine,
  Nitrogen, Chlorine and Bromine