Answer: two elements and three atoms
Explanation:
An element is the simplest substance and hence cannot be broken down using chemical reactions.
Magnesium chloride 
is an ionic compound formed by the transfer of electrons from element magnesium (Mg) to element chlorine (Cl) where Magmesium forms a cation 
by losing two electrons and chlorine forms an anion 
by gaining electron.
There are 3 atoms in Magnesium chloride which include one atom of magnesium (Mg) and two atoms of chlorine (Cl).
Answer:
Explanation:
H = 1
C = 12
O = 16
Acetylene, HC≡CH = 2+24 = 26
H2O = 2 + 16 = 18
In XS oxygen, one HC≡CH yields one H2O
26 g HC≡CH ==> 18 g H2O
2000 g HC≡CH ==> 2000*18/26 g H2O = 1384.6154 g H2O
