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.

the answer is 0.8m.

by: nicholas

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.