S=50.05/32 O=49.95/16, S=1.5640625/1.5640625 O=3.121875/1.5640625, S=1 O=1.99, S=1 O=2 Empirical Formula= SO2
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: The lowest pressure in a laboratory is 4.0×10^-11Pa
Using Ideal gas equation
PV = nRT
P= 4.0×10^-11Pa
V= 0.020m^3
T= 20+273= 293k
n=number of moles = m/A
Where m is the number of molecules and A is the Avogradro's number=6.02×10²³/mol
R=8.314J/(mol × K)
PV= m/A(RT)
4.0×10^-11 ×0.020 = m/6.02×10²³(8.314×293)
m = 4.0×10^-11×0.020×6.02×10^23 / (8.314×293)
m = 1.98×10^8 molecules
Therefore,the number of molecules is 1.98×10^8
Good morning
Chemical reactions can be detected by changes in : Temperature and color
Enjoy your day !
