Write the identity of the missing nucleus for the following nuclear decay reaction: 224 88ra→42he+?

Because the sums of both the top and bottom numbers (the mass number and atomic numbers) of each side must be equal, we know that in A the atomic number must be 2 because 88+2=90 and the mass number must be 4 so 228+4=232. Thus, because the atomic number is 2, you know this is helium and the nuclide is 4/2 He. This is a classic example of alpha decay. 

In letter B, the same concept can be applied, except the helium nuclide is given. The atomic number must be 86 so 86+2=88 and the mass number must be 220 so 220+4=224. Because 86 is the atomic number of radon, the nuclide is 220/86 Rn. 

For letter C, the gamma emission can be ignored as it has no mass. The mass number must be 4+237=241 and the atomic number must be 2+93=95. Because 95 is the atomic number of americium, the nuclide is 241/95 Am. 

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .