Rationale
Potassium, atomic number 19, is most likely to become a cation.
Potassium has a single electron in its outermost shell, making it highly inclined to lose that electron and form a positively charged ion (cation). This tendency is due to its position in Group 1 of the periodic table, where elements readily lose electrons to achieve a stable electron configuration.
A) Potassium, atomic number 19
Potassium is in Group 1 of the periodic table, which means it has one valence electron. Its low ionization energy allows it to easily lose this electron, resulting in the formation of a cation with a charge of +1. This characteristic makes potassium one of the most reactive metals, especially with nonmetals.
B) Oxygen, atomic number 8
Oxygen has six electrons in its outer shell and requires two additional electrons to achieve a stable octet configuration. While it tends to gain electrons to form anions (negatively charged ions), it is not likely to lose electrons to become a cation, as its electron affinity encourages the opposite behavior.
C) Fluorine, atomic number 9
Fluorine has seven electrons in its outer shell and is highly electronegative, meaning it readily gains an electron to complete its octet and form a -1 anion. Similar to oxygen, fluorine is more likely to gain electrons rather than lose them, making it unfavorable for it to become a cation.
D) Helium, atomic number 2
Helium is a noble gas with a complete outer shell of two electrons, which makes it chemically inert and very stable. Noble gases do not easily gain or lose electrons, so helium is not likely to form a cation under normal conditions.
Conclusion
Potassium's propensity to lose its single valence electron to form a cation distinguishes it from the other options, which either gain electrons or are stable due to complete electron shells. Understanding the likelihood of an atom becoming a cation is crucial in predicting its chemical behavior and reactivity in various reactions.
