Question

Which missing item would complete this alpha decay reaction?

`""_(98)^(251) "Cf" -> ""_(96)^(247) "Cm" + "___"`

`A.` `""_(-1)^(0) "e"`

`B.` `""_(97)^(247) "Bk"`

`C.` `""_(2)^(4) "He"`

`D.` `""_(92)^(238) "U"`

`E.` `""_(0)^(0) gamma`

Answer 1

`"Option" C-> ""_2^4He`

Explanation:

`"The decay would have helium left after the reaction."`

`""_98^251 Cf → ""_96^247Cm +""_2^4He`

`"We know the atomic masses of the elements but we do not know"`
`"know the number of protons of the substances ."`
`" But for this reaction number of neutrons are also required "`

First determine the number of neutrons in Cf

`"no. of neutrons = atomic weight - no. of protons"`

`"251 - 98 = 153 neutrons"`

Then determine the number of neutrons in Cf

`"no. of neutrons = atomic weight - no. of protons"`

`"247 - 96 = 151 neutrons"`

This means there are more 2 protons and neutrons

`"Decay in neutrons"`

`98 → 96 + 2`

`"Decay in protons"`

`153 → 151 + 2` helium atom as the electrons are number of electrons = no. of protons

Energy can be neither created nor destroyed .

Protons and neutrons are energy in scientific words

As energy cannot be destroyed so 251 → 247 cannot happen and there should be something more .

This is an alpha decay equation so this means there are more 2 electrons and neutrons which mean that the element is Helium without its electrons.An
α
particle is 2 protons and 2 neutrons bound together like they are within the nucleus of a Helium atom; it is so like a Helium nucleus that it is often written as `4/2He2+`