Stability of atoms is determined by neutron:proton ratio. This n/p ratio is 1:1 for elements below atomic number 20. Hope this helps.
Answer:
The right answer is "8.81 atm".
Explanation:
Given:
V = 5.00 L
Mass = 4900 g
MW = 32 g/mol
T = 350 K
Now,
Number of moles will be:



By using the ideal gas equation, we get
⇒ 
or,
⇒ 
By substituting the values, we get


Each isotope of Oxygen has a different number of neutrons
<h3>Further explanation
</h3>
The elements in nature have several types of isotopes
Atomic mass is the average atomic mass of all its isotopes
Isotopes are atoms has the same number of protons but has a different number of neutrons.
So Isotopes are elements that have the same Atomic Number (Proton)
Some of the isotopes of oxygen are:

Each isotope has 8 protons and 8 electrons but has a different number of neutrons
For O-16: number of neutrons = 16-8 = 8
For O-17: number of neutrons = 17-8 = 9
For O-18: number of neutrons = 18-8 = 10
Argon is a noble gas. Argon has a full outer shell. This makes it so that it does not need to react with any of the other elements to be stable.
With Rubidium and Cobalt its a whole different story.
I hope that helps!