Question

Which atom or ion is the largest? A.K B. K+ C. Ca D. Ca2+ E. Li

Answer 1

The neutral potassium (K) atom is the largest among the given options because it has more electron shells than the others and loses no electrons unlike its ionised form K+ or compared to Ca and Ca2+.

Step-by-step explanation:

The size of an atom or ion is influenced by the number of electrons and the effective nuclear charge. Atoms generally become smaller as you move across a period from left to right in the periodic table due to an increase in the positive charge of the nucleus, which pulls the electrons closer. Meanwhile, as you move down a group, atoms become larger due to the addition of electron shells. In this specific question, the largest entity would be the neutral K (potassium) atom since it has more electron shells compared to K+ (which has lost an electron and thus has a reduced radius due to a greater effective nuclear charge), Ca (calcium), and Ca2+ (which has lost two electrons, making it even smaller than the neutral atom). The Li (lithium) atom is smaller than potassium because it has fewer electron shells.

Answer 2

Consequently, the ion with the greatest nuclear charge (Al 3 +) is the smallest, and the ion with the smallest nuclear charge (N 3−) is the largest. The neon atom in this isoelectronic series is not listed in Table 2.8.3, because neon forms no covalent or ionic compounds and hence its radius is difficult to measure.