Question

question 27 (1 point)
what element in the second period has the largest atomic radius?
◯ a carbon
◯ b potassium
◯ c neon
◯ d lithium

question 28 (1 point)
which of the following factors contributes to the increase in atomic size within a group in the periodic table as the atomic number increases?
◯ a fewer electrons in the highest occupied energy level
◯ b an increase in number of protons
◯ c an increase in size of the nucleus
◯ d more shielding of the electrons in the highest occupied energy level

question 29 (1 point)
which of the following elements has the smallest atomic radius?
◯ a bromine
◯ b sulfur
◯ c chlorine
◯ d selenium

Explanation:

• Question 27: In a period, atomic radius decreases from left to right. Lithium (\(Li\)) is on the far - left of the second period. Carbon (\(C\)) is to the right of \(Li\), neon (\(Ne\)) is a noble gas (though atomic radius trends for noble gases are a bit different in terms of measurement, but still \(Ne\) has a smaller radius than \(Li\) in the context of period trends). Potassium (\(K\)) is in the fourth period.
• Question 28: As atomic number increases within a group, the number of electron shells increases. The inner electrons shield the outer electrons (in the highest occupied energy level) from the nuclear charge more effectively. Fewer electrons in the highest occupied energy level is incorrect as electron number in the outer shell is the same within a group. An increase in protons and nucleus size would tend to pull electrons in (if shielding was constant), but shielding dominates for group - wise atomic size increase.
• Question 29: In a group, atomic radius increases from top to bottom. Bromine (\(Br\)) and selenium (\(Se\)) are below sulfur (\(S\)) and chlorine (\(Cl\)). In a period, atomic radius decreases from left to right. Chlorine (\(Cl\)) is to the right of sulfur (\(S\)) in the third period.

Answer:

• Question 27: d. lithium
• Question 28: d. more shielding of the electrons in the highest occupied energy level
• Question 29: c. chlorine