Which of the following involves a transfer of electrons? pcl3 + cl2 → pcl5 co2 + 2lioh → li2co3 + h2o fecl2 + 2naoh → fe(oh)2 + 2nacl naoh + hcl → nacl + h2o

Answer is: PCl3 + Cl2 → PCl5.

Balanced chemical reaction: PCl₃ + Cl₂ → PCl₅.

Oxidation half reaction: P⁺³ → P⁺⁵ + 2e⁻.

Reduction half reaction: Cl₂ + 2e⁻  → 2Cl⁻.

In this chemical reaction phosphorus lost two electrons and change oxidatation number from +3 to +5; chlorine gain those two electrons and change oxidation number form 0 to -1.

In other chemical reactions, elements do not change oxidation numbers.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.