Download Chemistry: The Nature of Matter

Chemistry: The Nature of Matter

Atoms
 Smallest unit of matter
 Composed of subatomic particles
o ___________________________________________________
o ___________________________________________________
o ___________________________________________________
 Neutrons and protons have about the same mass and pack together to
form the atomic nucleus at the center of the atom
_________________________________________________________
 Electrons are in constant motion; are attracted to the + charged nucleus
but are outside of the nucleus
 _________________________________________________________
____________________________________________________________
____________________________________________________________

Atomic Number and Atomic Weight
 ____________________________________________________________
_______________________________________________________ (also,
since there are equal numbers of protons and electrons in an atom, the
atomic number also tells the # electrons)
 ____________________________________________________________
____________________________________________________________
 ____________________________________________________________
(# protons + # electrons = # neutrons)
Example: Carbon
o Atomic number = 6 (6 protons, 6 electrons)
o Atomic weight = 12.011
o Mass number = 6 neutrons

Energy Levels of Electrons
 ____________________________________________________________
____________________________________________________________
 More distant an electron is from the nucleus, the greater the energy
possible in the atom
 Different states of energy are called energy levels or electron shells
o 1st shell is closest to the nucleus, has the lowest energy, and holds
only 2 electrons
o 2nd shell has a little more energy and holds 8 electrons
o 3rd shell has even more energy, etc.
 ____________________________________________________________
____________________________________________________________
____________________________________________________________
 Electron configuration – where electrons are within the atom
Example: Oxygen – atomic number of 8, with 6 valance electrons

Elements
 ____________________________________________________________
____________________________________________________________
 Periodic Table of Elements
 Over 100 elements known, but only about 2 dozen commonly found in
living systems

Isotopes
 ____________________________________________________________
____________________________________________________________
Example: isotopes of carbon can have 6, 7, or 8 neutrons
 Isotopes identified by mass numbers – weighted averages of the masses of
an element’s isotope = atomic mass
o “Weighted” means abundance of each isotope in nature is
considered when average is calculated
o Carbon-12 is most abundant, thus Carbon’s atomic mass is 12.011
 All isotopes of an element have the same chemical properties

Radioactive Isotopes
 Some isotopes have unstable nuclei that break down at a constant rate over
time – this “break down” can give off radiation
 Use of radioactive isotopes:
o ______________________________________________________
o ______________________________________________________
o ______________________________________________________

Chemical Compounds
 ____________________________________________________________
____________________________________________________________
 Chemical formulas used to write compounds
Example: H2O, NaCl
 ____________________________________________________________
____________________________________________________________
Example: H = gas, O = gas; H2O = liquid