Chemistry of Life: Atoms, Ions, Molecules, and Water

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Chemistry of LifeAtoms, Ions, Molecules, and
Water
August 13 14 Lecture and Lab Rotations
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Atoms

• Matter- any substance that has mass
• Matter is composed of small particles called
  atoms.

Difference between mass and weight Mass refers
to the amount of a substance, whereas weight
refers to the force of gravity on the substance.
EX walking on the moon
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Example of an atom Carbon

• Carbon is an essential atom for life.
• It can assemble into DNA, proteins, carbohydrates
  and lipids, making complex life possible.

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Carbon

• Atomic mass is the number of protons and neutrons
  in the nucleus of the atom. Carbon is 12.
• Atomic number is the number of protons in the
  nucleus. Carbon is 6.
• Carbon is a neutral atom.

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Element

• Atoms with the same atomic number (same number of
  protons) have the same chemical properties and
  belong to the same element.

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Energy the ability to do work

• Electrons are negatively charged and carry the
  ability to be attracted to the positively charged
  nucleus, and repelled by the negative charge of
  other electrons.

• When an electron moves toward the nucleus it
  releases energy, and absorbs energy when it moves
  away from the nucleus.

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Electron Shells

• Electron shells are where the energy of the atom
  is stored.
• Orbital is the volume of space around a nucleus
  where an electron is most likely to be found.
  Each electron shell has a specific number of
  orbitals, and each orbital can only hold up to
  two electrons.

Since carbon has 6 electrons, how many shells
(and electrons on each shell) does it have?
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Ions

• An atom can gain or loose electrons from its
  outer shell.
• An ion is when the number of electrons and the
  number of protons is not equal because the atom
  has gained or lost an electron.

A sodium atom becomes a sodium ion when it looses
an electron because the nucleus is left
unbalanced and becomes positively charged.
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Isotopes

• An isotope is an atom that has the same number of
  protons but different number of neutrons.
• The number of neutrons in an atom of a particular
  element can vary without changing the properties
  of the element.
• Isotopes have the same atomic number, but
  different atomic mass.

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Molecules

• A molecule is a group of atoms held together by
  energy.
• A chemical bond is the energy or force that holds
  two atoms together.

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Ionic Bond

• When atoms are attracted to each other by
  opposite electrical charges.
• 2 key properties strong and non-directional

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Covalent Bond

• A strong chemical bond when that forms between
  two atoms when they share electrons.
• Why do atoms in molecules share electrons?
• Single, double (two pairs of electrons are
  shared), triple covalent bonds.
• Carbon has 4 electrons in outer shell and can
  form as many as 4 covalent bonds.

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Hydrogen Bonds

• Form when the positive end of one polar molecule
  is attracted to the negative end of another polar
  molecule.
• Are weak chemical bonds and one nucleus may be
  better at attracting the shared electron than the
  other and spend more time in the vicinity of the
  more strongly attracted atom.
• Characteristics highly directional and create
  tight bonds through the effect of many weak
  interactions.

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Hydrogen bonds give water unique properties

• Heat storage- it takes water a long time to boil
  and cool
• Ice formation- Why is ice less dense than water?
• High heat of vaporization- water can evaporate
• Cohesion (ability to bind to other polar
  molecules that are water when this polar
  substance is not water, it is adhesion)
• High polarity- hydrophilic and hydrophobic