Periodic Trends: Quiz

Periodic Trends: Quiz

7 questions

1. Question 1EasyWhich atom has the largest atomic radius?

   ALiBNaCKDCl
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   Answer: K

   Radius increases down a group. K is below Li and Na in group 1, and Cl is far to the right in period 3.

2. Question 2EasyWhich element has the highest first ionization energy?

   ALiBCCFDNa
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   Answer: F

   Ionization energy increases across a period and decreases down a group. F is furthest right in period 2.

3. Question 3MediumWhy do atoms get smaller across a period?

   AThey lose electron shellsBEffective nuclear charge increases while the outer shell stays the sameCNeutrons pull the electrons inwardsDElectrons repel each other less
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   Answer: Effective nuclear charge increases while the outer shell stays the same

   Protons are added but the number of inner electrons stays the same, so the outer shell is pulled in more tightly.

4. Question 4MediumWhich ion is the smallest?

   A$\ce{O^2-}$B$\ce{F-}$C$\ce{Na+}$D$\ce{Mg^2+}$
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   Answer: $\ce{Mg^2+}$

   All four have 10 electrons. Mg²⁺ has the most protons (12), so it pulls its electrons in most tightly.

5. Question 5MediumWhich is the correct order of increasing electronegativity?

   AF < O < N < CBK < Na < Li < FCCl < Br < IDO < N < Na
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   Answer: K < Na < Li < F

   Electronegativity decreases down group 1 (K 0.82 < Na 0.93 < Li 0.98), and fluorine is the highest of all (3.98).

6. Question 6HardThe first ionization energy of oxygen is lower than that of nitrogen. Why?

   AOxygen has fewer protonsBOxygen's outer electron is in a new shellCOxygen has a paired 2p electron, and the repulsion makes it easier to removeDNitrogen has a full outer shell
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   Answer: Oxygen has a paired 2p electron, and the repulsion makes it easier to remove

   N (2p³) has three unpaired electrons; in O (2p⁴) one orbital holds a pair, and the extra repulsion lowers the ionization energy.

7. Question 7MediumUsing $Z_\text{eff} \approx Z - S$, estimate the effective nuclear charge felt by a valence electron of chlorine (Z = 17).

   A1B7C10D17
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   Answer: 7

   Chlorine has 10 inner electrons (a [Ne] core), so $Z_\text{eff} \approx 17 - 10 = 7$.