Answer:
Bohr's model of the hydrogen atom is based on three postulates: 
1) An electron moves around the nucleus in a circular orbit, 
2) An electron's angular momentum in the orbit is quantised, 
3) The change in an electron's energy as it makes a quantum jump from one orbit to another is always accompanied by the emission or absorption of a photon. Bohr's model is semi-classical because it combines the classical concept of electron orbit (postulate 1) with the new concept of quantisation ( postulates 2 and ).
 
        
             
        
        
        
Answer:
0.179kg/m3 hope that helps you out 
 
        
             
        
        
        
Explanation:
(A)role of nittogen fixing bacteria
=Nitrogen-fixing bacteria, microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen (inorganic compounds usable by plants). More than 90 percent of all nitrogen fixation is effected by these organisms, which thus play an important role in the nitrogen cycle.
B)role of nitrifying bacteria 
=Nitrifying bacteria convert the most reduced form of soil nitrogen, ammonia, into its most oxidized form, nitrate. In itself, this is important for soil ecosystem function, in controlling losses of soil nitrogen through leaching and denitrification of nitrate.
C)role of denitrifying bacteria 
=Denitrifying bacteria converts nitrates back to nitrogen gas.
 
        
             
        
        
        
Answer:
This is how
Explanation:
<em>Protons and neutrons have approximately the same mass, but they are both much more massive than electrons (approximately 2,000 times as massive as an electron). The positive charge on a proton is equal in magnitude to the negative charge on an electron.</em>
 
        
                    
             
        
        
        
There is a total of 2 atoms in PoCl. One Cl (chlorine) and one Po ( Polonium)