Slide 1

Unit 1 Chemistry of Life: Atoms
and Molecules
Elements Required for Life
 Approx 25 elements
 C, O, H and N  96% of living matter
 P, S, Ca and K  4% of an organism’s weight
 Trace elements
 Needed in minute quantities
 Ex. Fe, I, Mg
 Anything that takes up space and has mass
 Solid, liquid, gas
 Elements cannot be broken down further
 Fe, Rb, Fr
 Compounds consist of two or more elements
 NaCl, H2O, H2CO3
Periodic Table of Elements
 Groups
 Periods
 Atomic
Atomic mass
Chemical Families
Alkali metals
Alkaline earth metals
Noble gases
Transition metals
Actinide/Lanthanide Series
Atomic Structure
 Atom-Smallest unit of matter
 Subatomic particles-Parts of atom
mass=1.7X10-24 g
(1 Da or amu)
Mass of electron is
Atomic Number and Weight
 All atoms of an element have same number of protons;
this is atomic number
 All atoms have a balanced charge, therefore:
Atomic number=Protons=Electrons
 Mass number=Protons + neutrons (round mass #)
 Mass number – atomic number (protons)=Neutrons
 All of atom’s mass is in nucleus; this is atomic weight
 Atoms of a given element that
contain different number of
neutrons, but same protons
 All natural elements exist as a
mixture of all its isotopes
 Some are radioactive isotopes
which have a spontaneously
decaying nucleus
Energy Levels
 Each electron shell contains a
certain amount of energy (n)
As you move up the energy
e- moving up absorbs energy
e- moving down loses energy,
releasing heat
# e- in each level=2(n)2
For atomic structure:
Place neutrons and protons in
Arrange e- using 2n2
 The number of electrons that orbit the outermost
energy level
 This is equivalent to the charge
Chemical Bonding
 All bonding occurs in the outer shell of atoms (sharing of
valance e-)
 Types of bonds:
Covalent Bonds-Sharing of a pair of valence electrons by two atoms.
Non polar covalent: e- are shared equally (methane)
 Polar covalent: Unequal sharing of e-. One tends to pull harder (HCl
or water)
Ionic Bonds-Transfer of e- from the negative ion to the positive ion.
Ion-Element that loses or gains an electron
Hydrogen Bonds-Hydrogen atoms bonded to electronegative atoms
Van Der Waals Interactions-All atoms and molecules when close to
each other tend to “stick” to one another. Occurs due to natural
gravitational forces of atoms

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