Periodic Law
When the elements are arranged in order of
increasing atomic number, there is a periodic
repetition of their physical and chemical
properties
Atomic Radius
One-half the distance between the nuclei in a
molecule consisting of identical atoms
Ionization Energy
The energy required to remove an electron
from a gaseous atom
Electronegativity
The tendency for an atom to attract electrons
to itself when it is chemically combined with
another element.
Ionic Radius
The atomic radius of an ion. The radii of
cations and anions decrease from left to right
across a period. They increase from top to
bottom in a group.
Laboratory 2 – Plotting
Periodic Trends
This is a “dry lab.” This means that you will
not be working with any chemicals. You will
be taking data that has already been
collected and interpreting it.
The data you will be interpret will be the
known values for the elements for the
periodic trends of first ionization energy and
atomic radius.
Laboratory 2 – Plotting
Periodic Trends
Procedure – For the laboratory you will make four
graphs, then answer four questions.
Graph 1 - For elements 3-20 graph atomic radius
as a function of atomic number. This means, plot
atomic number on the X axis and atomic radius on
the Y axis.
After creating the graph, use a colored pen or
pencil to draw a vertical line that represents that
beginning of each period (horizontal row on the
periodic table).
Laboratory 2 – Plotting
Periodic Trends
Graph 2 - For elements in Group 1 (Alkali metals),
make a graph of atomic radius as a function of
atomic number. Make a second line on this same
graph that will represent Group 2 (Alkaline Earth
Metals).
Use a periodic table to determine
which elements are members of Group 1 and
which elements are members of Group 2.
Laboratory 2 – Plotting
Periodic Trends
Graph 3 - For elements 3-20, make a graph of the
energy required to remove the easiest electron
(first ionization energy) as a function of atomic
number. Plot atomic number on the X axis and
energy required on the Y axis.
After creating the graph, use a colored pen or
pencil to draw a vertical line that represents that
beginning of each period (horizontal row on the
periodic table).
Laboratory 2 – Plotting
Periodic Trends
Graph 4 - For elements of Group 1 (Alkali metals),
make a graph of the energy required to remove the
easiest electron (first ionization energy) as a
function of atomic number. On the same graph
make a second line to represent Group 2 (Alkaline
Earth Metals).
Use a periodic table to determine which elements
are members of Group 1 and which elements are
members of Group 2.
Laboratory 2 – Plotting
Periodic Trends
QUESTIONS FOR DISCUSSION:
1. What happens to the atomic radius as the atomic
number increases across a period? Down a group?
2. What happens to the energy needed to remove
an electron as the atomic number increases across
a period? Down a group?
3. Why does atomic radius change as it does?
4. Why does the energy required to remove an
electron change as it does?