Vanadium has an atomic mass of 50.9415 amu. it has two common isotopes. one isotopes has a mass of 50.9440 amu and a relative abundance of 99.75% .

Isotope simply means one of the forms of a chemical element. The mass of the second isotope of vanadium is 49.944 amu

Given that:

--- atomic mass of vanadium

---- the mass of the first isotope

---- the relative abundance of the first isotope

The following equation can be used to calculate the mass of the second isotope.

Where:

So, we have:

Collect like terms

Solve for

Hence, the mass of the second isotope is 49.944 amu

Read more about isotopes at:

link

indium, and thallium have three electrons i think

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.