Which element has the smallest radius?

Answer 1

Atomic radii decrease across a Period, but increase down a Group, so the element should be #He#.

Thus, helium would be our predicted smallest element based on the spray above.

Nevertheless, given that we are physical scientists we should consider the data, and see if it confirms our prediction. This site lists the atomic radius of hydrogen as #0.37# #"pm"#, and of helium as #0.31# #"pm"#; #1# #"pm"# #=# #1xx10^-12m#; inorganic chemists tend to use Angstroms, #1xx10^-10m#, but I can never find the Angstrom symbol, a capital "A" with a circle hat).

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Answer 2

Cooper Anderson

The element with the smallest radius is helium.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.