Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

To achieve an outer octet, what must an atom of element 19 do?

1. Add an electron and acquire a charge of -1

2. Lose an electron and acquire a charge of +1

3. Share electrons equally with another atom

4. Gain two electrons and remain neutral

The correct answer is: Lose an electron and acquire a charge of +1

An atom of element 19 corresponds to potassium (K), which has an atomic number of 19. To achieve a stable outer octet, potassium must seek to mimic the electron configuration of the nearest noble gas, which is argon (Ar). Potassium has one electron in its outermost shell (the 4th energy level). Since the goal is to complete the outer shell to an octet, potassium can achieve this by losing that one outer electron. By doing so, potassium will adopt a configuration similar to argon, resulting in a full outer shell of eight electrons in the lower energy level (3rd shell). This loss of an electron gives potassium a charge of +1 because it now has more protons than electrons. This process is typical for alkali metals like potassium, which readily lose their single outer electron to attain a more stable electron configuration, similar to the noble gases. Other options present different scenarios that do not align with the behavior of potassium in pursuit of a full outer octet.