Equation is as follow,
<span> 4 Na (s) + O</span>₂ <span>(g) → 2Na</span>₂<span>O (s)
According to equation,
91.92 g (4 moles) of Na produces = 123.92 g (2 moles) of Na</span>₂O
So,
17.4 g of Na will produce = X g of Na₂O
Solving for X,
X = (17.4 g × 123.92 g) ÷ 91.92 g
X = 23.45 g of Na₂O
207 is the mass number. 82 would be the atomic number
Protons are held inside nucleous with neutrons with large amount of force. So mere rubbing doesn't help in breaking the nucleous of an atom. But electrons are far from the nucleous and the force of attraction is smaller. So electrons can jump readily while protons can't
Down...
and if you were wondering, the earth pushes back
Answer : The time passed in years is 
Explanation :
Half-life = 5730 years
First we have to calculate the rate constant, we use the formula :



Now we have to calculate the time passed.
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 
t = time passed by the sample = ?
a = let initial amount of the reactant = X g
a - x = amount left after decay process = 
Now put all the given values in above equation, we get


Therefore, the time passed in years is 