Question

rank the following species by radius, from largest to smallest: $cl^{-}$, $k^{+}$, $ca^{2}$, ar, $s^{2-}$.
$\bigcirc$ ar, $k^{+}$, $ca^{2+}$, $s^{2-}$, $cl^{-}$
$\bigcirc$ $s^{2-}$, $cl^{-}$, ar, $k^{+}$, $ca^{2+}$
$\bigcirc$ $ca^{2+}$, $s^{2-}$, $cl^{-}$, ar, $k^{+}$
$\bigcirc$ ar, $k^{+}$, $cl^{-}$, $ca^{2+}$, $s^{2-}$

question 4
which of the following elements have the most metal character?
$\bigcirc$ te
$\bigcirc$ i
$\bigcirc$ in
$\bigcirc$ ge

Explanation:

• For the first question (ranking species by radius):
• All the given species (\(Cl^-\), \(K^+\), \(Ca^{2 +}\), \(Ar\), \(S^{2-}\)) are isoelectronic (they have the same number of electrons, \(18\) electrons).
• For isoelectronic species, the more negative the charge (for anions), the larger the radius because the extra electrons increase electron - electron repulsion and decrease the effective nuclear charge experienced by each electron. The more positive the charge (for cations), the smaller the radius because there are fewer electrons and a higher effective nuclear charge pulling the remaining electrons closer to the nucleus.
• \(S^{2-}\) has the most negative charge among the anions, so it has the largest radius. \(Cl^-\) is less negative than \(S^{2-}\). \(Ar\) is a neutral atom. \(K^+\) is a cation with a \(+ 1\) charge, and \(Ca^{2+}\) is a cation with a \(+2\) charge (smallest radius among them).
• For the second question (most metal character):
• Metal character increases down a group and decreases across a period from left to right in the periodic table.
• \(Te\) (Tellurium) is in Group \(16\), \(I\) (Iodine) is in Group \(17\), \(In\) (Indium) is in Group \(13\), and \(Ge\) (Germanium) is in Group \(14\).
• Among these, \(In\) is the left - most and closer to the lower part (compared to \(Ge\) and \(Te\) in their respective groups) in the periodic table. So \(In\) has the most metal character.

Answer:

• First question: \(S^{2-},Cl^-,Ar,K^+,Ca^{2+}\)
• Second question: \(In\)