Student Exploration: Periodic Trends
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: atomic radius, electron affinity, electron cloud, energy level, group, ion, ionization energy, metal,
nonmetal, nucleus, period, periodic trends, picometer, valence electron
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. On the image at right, the two magnets are the same. Which paper
clip would be harder to remove?
b
2. Which magnet would be most likely to attract additional paper clips?
b
3. What is the relationship between the thickness of the book and the ability of the magnet to hold on to and
attract paper clips?
the thicker the book The ability of the magnet to hold onto and attract paper clips decreases
Gizmo Warm-up
Just as the thickness of a book changes how strongly a magnet attracts a paper clip, the
size of an atom determines how strongly the nucleus attracts electrons. In the Periodic
Trends Gizmo, you will explore this relationship and how it affects the properties of
different elements.
The atomic radius is a measure of the size of the electron cloud, or the region where
electrons can be found. To begin, check that H (hydrogen) is selected in Group 1 on the left. Turn on Show
ruler. To measure the radius, drag one end of the ruler to the proton in the nucleus and the other end to the
electron. Click Save radius to record the value.
1. What is the radius of hydrogen? 53 p.m.
Notice that the radius is measured in picometers (pm). A picometer is one
trillionth of a meter.
2. On the right side of the Gizmo, select Li. Connect the right side of the ruler to 167 p.m.
the outermost electron, or valence electron. What is the radius of lithium?
, Get the Gizmo ready:
Activity A:
● Check that Atomic radius is selected from the
Atomic radius
drop-down menu.
Question: What factors affect the radius of an atom?
1. Predict: How do you think the radius of an atom will change as you move down a group (vertical column) in
the periodic table?
it would get larger
2. Collect data: Use the ruler to measure the atomic radii of the group 1 elements. As you do so, count the
energy levels (shown as rings of electrons) in each atom. Record in the table.
Element H Li Na K Rb Cs
Number of energy
1 2 3 4 5 6
levels
Ato
53pm 167 pm. 190 p.m. 243pm 265pm 290pm
mic radius (pm)
3. Observe: What happens to the radius as you move down group 1?
it increases
4. Explore: Turn off Show ruler. Select L
i, and then select Be. Observe the radii of the elements in group 2.
Then look at other groups. What pattern do you see?
the radii keeps increasing as you go down the groups
5. Draw a conclusion: In general, what is the effect of the number of energy levels on the radius of an atom?
the more energy levels there are, the greater the radius of the atom is
6. Predict: How do you think the radius of an atom will change as you move across a period (horizontal row)
in the periodic table?
I think it will decrease
7. Collect data: Beginning with Na, record the number of energy levels, number of protons, and atomic radius
for each element in period 3.
Element Na Mg Al Si P S Cl Ar
Number of energy levels 3 3 3 3 3 3 3 3
Number of protons 11 12 13 14 15 16 17 18
Atomic radius (pm) 190p
m 144p 118p 111p 98pm 88pm 79pm 71pm
m m m
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