Answer
The answer is below.
Work Step by Step
From the periodic table, chlorine is a nonmetal. It has a tendency to form an anion. The atomic number of chlorine is 17. This suggests that it has 17 protons and 17 electrons. As chlorine has 17 electrons and needs only one electron to have a stable electronic configuration. Chlorine will gain one electron to form\[\text{C}{{\text{l}}^{-}}\]ion, with a total of 18 electrons.
From the periodic table, the atomic number of tellurium is 52; thus, the number of protons in tellurium is 52. The number of electrons is equal to the number of protons for a neutral atom. But, tellurium has 54 electrons, which means it gains 2 electron to have stable electronic configuration. The ion formed is \[\text{T}{{\text{e}}^{2-}}\].
From the periodic table, the atomic number of bromine is 35; thus, the number of protons in bromine is 35. The number of electrons is equal to the number of protons. But as the ion formed by bromine is \[\text{B}{{\text{r}}^{-}}\]
From the periodic table, the atomic number of strontium is 38, thus, the number of protons in strontium is 38. The number of electrons is equal to the number of protons. But, strontium has a charge of +2, which means it will lose two electrons. So, the number of electrons is 36.
