Answer:
To check if it's properly cleaned.
Explanation:
When you finish using a microscope, you have to take out all your samples you were using and make sure it is completely clean so that no further contamination affects future sample analysis.
Also when you begin to use it, make sure it is clean so that when you analyze your sample(s) are free from other unexpected agents.
Strontium atom loses 2 electrons to become an ion with 2 electrons lesser than its atom. Your answer is C.
Ok, I will help you answer but it is very hard to read could you enlarge it first?
Thanks!
Charge # = protons - electons
Mass # = protons + neutrons
so that would be
3-3= charge#
3+4= mass#