The potassium atom is indeed larger than the potassium ion. To understand why, we need to look at the structure of both. A potassium atom (K) has 19 protons and, in its neutral state, 19 electrons. When potassium loses one electron to become a potassium ion (K+), it loses its outermost electron, which is in the fourth energy level. This loss reduces the electron cloud’s size around the nucleus, resulting in a smaller ion.
Additionally, when an atom loses an electron, the remaining electrons experience a greater effective nuclear charge due to reduced electron-electron repulsion. This pull from the nucleus draws the remaining electrons closer, further decreasing the size of the potassium ion compared to its neutral atom counterpart.
In summary, the potassium atom is larger because it has more electrons than the potassium ion, which has lost one electron, resulting in a more compact structure.