Answer:
5 1 2 4and 3 this is correct way
The larger the piece the longer it will take to break down. This is because it has more mass that needs to be broken down.
Tc is Technetium, and it has an atomic number of 43. Its atomic configuration is [Kr] 5s(1) 4d(5) [I'm on my phone so I can't do numbers on shoulders, pretend that 1 and 5 are on the s and d's shoulder]
The outside most ring is the 4d(5), and the d orbital can hold ten electrons.
Valence electrons are electrons, in you could say the outside ring that isn't filled, the extra ones. In this case, there are 5.
