Answer:
1. Diagram C. 
2. Diagram A. 
Explanation:
1. Calcium atom, Ca has 20 protons and 20 electrons. On the other hand, Calcium ion, Ca^2+ has 20 protons and 18 electrons. This is true because the +2 charge on the calcium ion, Ca^2+ indicates that the calcium atom, Ca has loss 2 electrons. 
From the above illustration we can say that calcium ion, Ca^2+ has the following:
Proton = 20
Electron = 18
Therefore, diagram C indicates calcium ion, Ca^2+. 
2. Fluorine atom, F has 9 protons and 9 electrons. Fluoride ion, F¯ has 9 protons and 10 electrons. This is so because the –1 charge on the fluoride ion, F¯ indicates that the fluorine atom, F has gained 1 electron. 
Thus, we can say that the fluoride ion, F¯ has the following:
Proton = 9
Electron = 10
Therefore, diagram A represent fluoride ion, F¯.
 
        
             
        
        
        
You could observe stuff like how many inches of rain we got or how many flowers are growing or how was the weather Monday through Friday .also by looking outside of Simply observing the weather outside in the nature
        
             
        
        
        
Answer: The final pressure is 75 mm Hg.
Explanation:
According to Boyle's law, at constant temperature the pressure of a gas in inversely proportional to volume.
Since, it is given that the temperature is constant. Hence, formula used is as follows.

Substitute the values into above formula as follows.

Thus, we can conclude that the final pressure is 75 mm Hg.
 
        
             
        
        
        
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