GRAPHING TRENDS IN PERIODIC TABLE ASSIGNMENT:
RESPONSE EXEMPLAR OF OBSERVATIONS AND ANALYSIS QUESTIONS.
..MODEL OF ONE OF THE GRAPHS… only one graph shown for illustration….
NOTICE CORRECT TITLE, LABELS AND UNIT FOR X AND Y AXIS.
Atomic Radius as a periodic function of Atomic Number
2.5
Atomic
2
Radius in
1.5
Angstroms
1
(=.1
0.5
nanometer)
0
Radius
0
10
20
30
Atomic Number
OBSERVATIONS
1.
What happens to the atomic radius as the atomic number increases across a period? Down a family?
a. As shown in the graph, the atomic number decreases across a period as the atomic number increases.
It increases when a new period is started and then again decreases across that new period.
b.
2.
The atomic radius increases down each family as the atomic number increases in family IA & IIA.
What happens to the energy needed to remove an electron as the atomic number increases across a
period? Down a family?
a. The energy needed (ionization energy) increases across a period as atomic number increases and
b. The energy needed decreases down family’s IA & IIA as atomic number increases
Conclusion (Analysis)
1.
2.
3.
What properties of the elements are periodic functions of their atomic numbers?
Based on the evidence shown in the graph, the atomic radius and the amount of energy needed to remove
an electron are periodic functions of the atomic numbers. The radius decreases periodically across each
period and down each family. Also shown in the graphs, the ionization energy increases across each
period repeatedly and decrease down both family IA and IIA.
Why does the atomic radius change as it does?
As atomic number goes up across a period, the number of electrons and protons increase. This increase
causes an increase in the attractive force between positive force of the nucleus and the negative charges
of the electrons in the energy levels. The attractive force reduces the radius as it increases across the
periods. The radius increases down a family because energy levels are added increasing the distance the
electrons are from the nucleus in the new energy levels.
Why does the ionization energy change as it does?
As the atomic number goes up, the number of electrons and protons increase across a period increasing
the attractive force of the nucleus (protons) on the electrons in the energy level. The increasing attraction
requires more energy to remove an electron from the nucleus. Down the family, the number on energy
levels increases at each new period moving the negative electrons farther away from the positive nucleus.
Moving farther away reduces the attractive force making it easier, less electron volts, to remove an
electron.