A = mass number, A = protons + neutrons
Z = atomic number, Z = protons
neutrons = A - Z
neutrons = 18 - 8 = 10
1kg of water has greater internal energy compared to 1g of water because 1kg of water has more mass.
Answer:
16.06 L was the initial volume of the balloon.
Explanation:
Initial moles of freon in ballon = 
Initial volume of freon gas in ballon = 
Moles of freon gas added in the balloon = n = 3.50 mole
Final moles of freon in ballon = 
Final volume of freon gas in ballon = 
Using Avogadro's law:
( at constant pressure and temperature)

16.06 L was the initial volume of the balloon.
They are found in group 3 of the periodic table.