Question

This graph shows two curves pertaining to a hydrogen s orbital.

Answer 1

Th graph of the s orbital of hydrogen is bell shaped. For the first energy level, the peak of the graph is around 1 micron. In the next energy level, there is a higher radial probability density at a further distance from the nucleus. This trend continues for the next energy levels.

Answer 2

Answer 1) : According to the complete question attached in the answer,

The radial wave function  which is denoted by $R_{nl}(r)$ shown with orange color crosses through zero point. Also, At the the radial nodes, which are spherical shells to some radial distance away from the nucleus there no electron are found.

Also, the radial probability distribution curve denoted as $R^{2}_{nl}(r)$ shown in  blue  color is observed to touch zero, and shows the place of radial node.

Therefore, the total number of nodes will include both the kinds  which has radial and angular nodes which will be represented by 'n'.

It is observed that for any atomic orbital, the total number of nodes will be n-1  .

Considering the s orbital of the hydrogen, which has zero angular momentum  (l); (l=0), as it has zero angular nodes.  

Hence, there will be only radial nodes, which is

(n−1  =  total number of radial nodes in s orbitals)

According to the image, there are 4  radial nodes shown, so n  =  5  (as n-1 = 4; therefore, n = 5)

This represents the 5s orbital.

Answer 2) The radial nodes are observed in I'm seeing radial nodes at  

$1.9a_{0}$,  $6.4a_{0}$,$13.9a_{0}$ and  $27.0a_{0}$.

where  $a_{0}$ represents the  hydorgen bohr atomic radius =  0.0529177 nm

Explanation : It is quite easy to observe the given graph and find out the approximate values of the radial nodes, it does not requires any equation to be solved. Equation can be used to find the radial nodes if it was supplied along with the question. Although by mere speculation one can find out the answer.