Acovalent bond forms
a. when an element becomes a noble gas.
b. when atoms share electrons.
c. between metals and nonmetals.
d. when electrons are transferred from one atom to another.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

increased stability in the completion of fluorine's outer shell.

a polar bond is formed when electrons are shared unevenly between atoms

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).