[21385]

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

[Yggdrasil]

Since Be²⁺ has only one electron, you can treat it as a hydrogen atom with Z = 3.

[21385]

Doesn't Be(2+) have the same number of electrons as a helium atom, not a hydrogen atom?
also, can someone tell me the formulas? because I don't seem to learned this formula at all
Thanks a lot

[Yggdrasil]

Ah, my bad.  I don't know if there are simple equations you can use for a helium-like atom.  The problem would be much simpler for Be₃₊ since you could use the equations for the hydrogen atom.