Question #a14c2

1 Answer
Jul 20, 2017

Answer:

#9 * a_0#

Explanation:

All you need to know in order to answer this question is that the radius of an orbit depends on the principal quantum number, #n#, that describes the energy level on which the electron is located.

http://hyperphysics.phy-astr.gsu.edu/hbase/hyde.html

If you take #a_0# to be the Bohr orbit, you can say that you have

#r_n = n^2 * a_0#

In your case, the third orbit is characterized by

#n = 3#

so you will have

#r_3 = 3^2 * a_0 = 9 * a_0#

http://jennarocca.com/bohr-radius-equation-derivation/