Question

name: ____________ block: ____________ progress check atomic radius and ion radius circle which atom or ion is larger and explain why. calcium vs potassium phosphorus vs antimony se vs se²⁻ mg vs mg²⁺

Explanation:

Calcium vs Potassium:

1. Consider periodic - table trends. Atomic radius increases from right to left across a period. Potassium (K) is in Group 1 and Calcium (Ca) is in Group 2 of the same period (Period 4). Potassium has one less proton than calcium but the same number of electron shells. The weaker nuclear - attraction on the outer electrons in potassium makes its atomic radius larger. So, Potassium is larger.

Phosphorus vs Antimony:

1. Atomic radius increases down a group. Phosphorus (P) is in Group 15 and Period 3, while Antimony (Sb) is in Group 15 and Period 5. Antimony has more electron shells than phosphorus. The addition of electron shells increases the atomic radius. So, Antimony is larger.

Se vs Se²⁻:

1. When an atom gains electrons to form an anion, the electron - electron repulsion increases. Selenium (Se) gains two electrons to form Se²⁻. The increased electron - electron repulsion causes the electron cloud to expand. So, Se²⁻ is larger.

Mg vs Mg²⁺:

1. When an atom loses electrons to form a cation, the electron - electron repulsion decreases and the nuclear attraction on the remaining electrons is stronger. Magnesium (Mg) loses two electrons to form Mg²⁺. The removal of two outer - shell electrons reduces the electron cloud size. So, Mg is larger.

Answer:

Potassium is larger than calcium because of weaker nuclear - attraction on outer electrons in the same period.
Antimony is larger than phosphorus due to more electron shells down the group.
Se²⁻ is larger than Se because of increased electron - electron repulsion in the anion.
Mg is larger than Mg²⁺ because of reduced electron cloud size when electrons are lost to form the cation.