Periodic Table – Elements and Electrons
Elements in the same group have similar properties
I.e. O, S, __, __
F, Cl, __, __
Electrons and Energy Levels
 The movement of electrons around the atom is restricted to
fixed regions of space
 These regions are 3 dimensional, like layers of an onion, and are
called energy shells or energy levels
 Energy levels are volumes of space in which an electron may be
found.
 Electrons move between energy levels or shells
o The _____ the energy level an electron is in the closer it is
to the nucleus and _______ energy it has
o The ______ the energy level an electron is in, the _____
energy it has
__ electrons can occupy the 1st energy level, ___ electrons occupy the
second and subsequent levels.
Bohr-Rutherford Diagrams and Lewis Structures
Elements are organized in the periodic table according to atomic
number but also according to the way in which the electrons occupy and
fill energy levels.
Bohr-Rutherford Diagrams-show electron energy levels and electron
occupancy
The outer shell/energy level is called the valence shell of the atom.
Lewis Structures – show valence shell electrons
Period Related Pattern of the Periodic Table
The number of energy levels that electrons occupy in an element = the
period number of that element
Period 1
Period 2
Period 3
Period 4
Group Related Pattern of the Periodic Table
 All the elements in the same groups, (groups 1, 2, 13-18), have the
same number of valence electrons
 Valence electrons are added/removed or shared between atoms
to form bonds with other elements
 Valence electrons are what are responsible for chemical
reactions.