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?
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
the outermost electron, or valence electron. What is the radius of lithium?
Activity A:
Get the Gizmo ready:
• Check that Atomic radius is selected from the
drop-down menu
Atomic radius
NOVA
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