Answer:
Mg- 27 means isotope with 12 protons and 15 neutrons.
Also 27 is mass number which express sum of protons and neutrons.
In nucleus one neutrn decays to electron and proton. Mass number remain same but Al-27 nucleus contain 13 protons and 14 neutrons. Electron is ejected out from nucleus.
<span>Mendeleev observed that tellurium has chemical properties like other elements in its group, and he did not know that neutrons cause the greater atomic mass is the most likely reason.</span>
50km / 2.5 = 20 km per hour
