Name two elements that have properties similar to those of beryllium and have average atomic masses higher than 130

In the periodic table, elements of the same group are characterized by having the same similar properties.
So, first we will check the elements that lie within the same group as beryllium  and then we will attempt to choose the elements with atomic mass higher than 130.

So, elements in the same group as beryllium are: magnesium, calcium, strontium, barium and radium.
Among these elements, we will find that:
radium has atomic mass of 226 amu
barium has atomic mass of 137.327 amu

Based on this, the two elements would be barium and radium.

Answer : option a) 84explanation :

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.