Which of the following elements would most likely become a positive ion when forming a chemical bond?
a. sulfur
b. helium
c. carbon
d. calcium

correct option will D.

Explanation:

Calcium belongs to the group 2 i.e. of alkaline earth metals in periodic table. electronic configuration of calcium is .

So in order to attain noble gas configuration calcium will loose its two electrons during chemical bond formation.

Sulfur is a non metal which forms negatively charged ion so as to complete ts octet during chemical bond formation.

Helium is a noble gas with fully filled electronic configuration.

Carbon forms bond which is covalent in nature.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.