The core of the 40 calcium atom, the most common isotope is symbolized by ₂₀⁴⁰ca. 1) indicate the composition of the atom of calcium. 2) calculate its mass. compare it to the core's one. what can you say ? mass of a nucleon : mnucleon = 1,67 x 10⁻²⁷ kg. mass of an electron : melctron = 9,11 x 10⁻³¹ 3) there are three other stable isotopes of calcium. knowing that they possess respectively two, three and four neutrons more than the calcium 40, to give the symbol of their core. 4) wich ion does it form ?

1) 20 protons, 20 electrons, 20 neutrons and so 40 nucleons

2) 40 x 1,67 x 10^-27 = 6.68 x 10^-26

This is the core's mass and the atom mass at the same time because the elctron's mass isn't important ( like 1/1000 of the mass )

3) ₂₀⁴²Ca        ₂₀⁴³Ca         ₂₀⁴⁴Ca

Those are the three one's.

4) It forms a cation.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.