1. The subscript when writing the notation is always dedicated to the atomic number of the element. Since the atomic number for Mercury, Hg, is 80, then the subscript is <em>80</em>.
2. For the second problem, you just have to balance out the subscripts and superscripts of the reactions.
Superscripts: 203 = 203 + ?; To balance, the missing number would be 0.
Subscripts: 80 = 81 + ?; To balance, the missing number would be -1.
<em>Hence the particle produced is actually an <u>electron</u>, or a <u>beta particle</u> (not an element). The <u>mass number is 0</u>, and the <u>atomic number is 0 </u>(since it does not contain any proton).</em>
Answer : The total mass of oxygen gas released in the reaction will be, 12.8 grams
Explanation :
Law of conservation of mass : It states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.
This also means that total mass on the reactant side must be equal to the total mass on the product side.
The balanced chemical reaction will be,

According to the law of conservation of mass,
Total mass of reactant side = Total mass of product side
Total mass of
= Total mass of 
or,
Total mass of
= Mass of
+ Mass of 
As we are given :
Total mass of
= 16.12 grams
The mass of
= 9.72 grams
So,
Total mass of
= Mass of
+ Mass of 


Therefore, the total mass of oxygen gas released in the reaction will be, 12.8 grams
Row: similarity in properties.
Column: Arrange according to the elements' masses and valency.
Water vapor
Its still water(H2O)
Just in the gas form
Answer:
7.0
Explanation:
second question is 4.90 third question is 3.0 fourth question is 6.6