Explanation:
An alpha particles is basically a helium nucleus and it contains 2 protons and 2 neutrons.
Symbol of an alpha particle is 
. Whereas a neutron is represented by a symbol 
, that is, it has zero protons and only 1 neutron.
Therefore, reaction equation when an aluminum- nuclide transforms into a phosphorus- nuclide by absorbing an alpha particle and emitting a neutron is as follows.
Mole is base unit of substance. The number of particles in one mole is equal to 6.022 × 10²³. The number of particle in a mole is called as Avogadro's number.
The mole of substance is the amount of substance that contain elementary particles as the number of atoms. the symbol of mole is mol. it is the SI unit of amount of substance. The number particles are ion one mole of substances is 6.022 × 10²³. The number of particles in one mole of substance is called as Avogadro's number.
Thus, Mole is base unit of substance. The number of particles in one mole is equal to 6.022 × 10²³. The number of particle in a mole is called as Avogadro's number.
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Answer: 20 mg Te-99 remains after 12 hours.
Explanation: N(t) = N(0)*(1/2)^(t/t1/2)
N(t) = (80 mg)*(0.5)^(12/6)
N(t) = 20 mg remains after 12 hours
