The nuclear radius formula is r = r0 A^(1/3), with r0 = 1.2 femtometres. What is the radius of an aluminum-27 nucleus?

1. Apply r = r0 A^(1/3) with r0 = 1.2 fm and A = 27. 2. The cube root of 27 is exactly 3, since 3 cubed equals 27. 3. Multiply: r = 1.2 x 3 = 3.6 fm. 4. 1.2 fm is just r0 itself, without multiplying by the cube root of A. 5. 2.4 fm and 4.8 fm do not match this multiplication. 6. So 3.6 fm is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.2 Nuclear Forces and Radioactivity_