Question 4

An atom with a positive charge has lost an electron.

When an atom has a positive charge, it indicates that it has lost one or more electrons, resulting in an overall positive charge due to the surplus of protons.

A) Gained an electron.

This option is incorrect because gaining an electron would result in a negative charge for the atom. An atom can only become positively charged by losing electrons, not by gaining them.

B) Lost an electron.

This option is correct because a positive charge in an atom signifies that it has fewer electrons than protons. The loss of an electron leads to a net positive charge.

C) Gained a proton.

This option is incorrect since adding a proton would increase the positive charge of the atom, leading to a higher atomic number and a different element altogether. Positive charge results from electron loss, not proton gain.

D) Lost a proton.

This option is also incorrect because losing a proton would decrease the atomic number and potentially change the identity of the atom. A positive charge arises specifically from the loss of electrons.

Conclusion

The correct answer, that an atom with a positive charge has lost an electron, accurately reflects the fundamental principles of atomic structure and charge. All other options misinterpret the relationship between protons and electrons, thus failing to explain the mechanism behind an atom's positive charge.