The single proton that forms the nucleus of the hydrogen atom has a radius of approximately 1.0×10−13cm. the hydrogen atom itself has a radius of approximately 52.9 pm what fraction of the space within the atom is occupied by the nucleus?

The answer is

6.8 * 10^-15

The explanation:

1- we have to convert all measurements to the same units:  

Conversions:  

when 1 m = 100 cm  

and 1 m = 10^12 pm  

So,

proton radius: 1.0*10^-13 cm * (1m / 100 cm) = 10^-15 m  

proton volume: 4/3 * pi * r^3 = 4/3 * pi * (10^-15 m)^3 = 4.2 * 10^-45 cu. meters  

and

H atom radius: 52.9 pm * (1m / 10^12 pm) = 5.29 * 10^-11 m  

H atom volume: 4/3 * pi * r^3 = 4/3 * pi * (5.29 * 10^-11 m)^3 = 6.2 × 10^-31 cu. meters  

So,

2- Fraction of space occupied by nucleus = proton volume / H atom volume  

= (4.2 * 10^-45 cu. meters) / (6.2 × 10^-31 cu. meters)  

= 6.8 * 10^-15  

So, the "fraction" would be 6.8 * 10^-15 out of 1.

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chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.