The question is in two parts.

a) Consider the n=3 state of the Be(2+) ion. What is the radius of the electron orbit of this ion, relative to the nucleus? a) 1.17Å (b) 1.18Å (c) 1.19Å (d) 1.20Å (e) 1.21Å

b) Consider the n=2 state of the Be(2+) ion. What is the velocity of the electron orbiting the nucleus, relative to the nucleus?

(a) 4.38 x 10^4 m/s (b) 4.38 x 10^5 m/s (c) 4.38 x 10^6 m/s

(d) 4.38 x 10^7 m/s (e) cannot be determined from given data

I basically have no idea what to do with these problems, it would be really great if someone could tell me the method to solve this problem. Thanks