The mass number of an atom is calculated by adding the number of protons and the number of neutrons together.
In this case, you have:
- Protons: 3
- Neutrons: 3
So, the mass number is:
3 (protons) + 3 (neutrons) = 6
However, you mentioned 4 yellow dots, which may indicate additional information, but typically dots are not used to represent protons or neutrons. If the yellow dots are supposed to represent electrons or if they are not relevant to finding the mass number, then the mass number remains 6.
Since the options given (7, 3, 4, 10) do not contain 6, if the yellow dots do represent an additional count (like a total atom count), we need clarification on their role. If there’s no indication they're part of the mass number calculation, then just keep it at 6.
If we must choose from the provided options and assume there might be an error or oversight, I'd guess the closest could be a) 7, if there was a misunderstanding and an additional area to count affecting the total.
But according to standard definitions of mass number: mass number = protons + neutrons = 6.
Please double-check the context of the yellow dots to clarify if they contribute to the atom's overall mass or if they represent something else entirely.