Periodic Trends and Atomic Properties (4E) - Chem & Physics

1. What is the periodic trend for electron affinity (more negative) when moving left to right across a period?

   Electron affinity becomes more negative across a period. Smaller radius and higher $Z_{\mathrm{eff}}$ stabilize added electron more effectively.

2. Which has the larger radius: Na or Na$^+$?

   Na has the larger radius. Neutral Na has one more electron than Na$^+$, increasing repulsion and size.

3. Which has the larger radius: Cl or Cl$^-$?

   Cl$^-$ has the larger radius. Cl$^-$ has an extra electron, causing greater repulsion and larger size than neutral Cl.

4. What is the periodic trend for atomic radius when moving left to right across a period?

   Atomic radius decreases across a period (left to right). Increasing effective nuclear charge pulls electrons closer without adding new shells.

5. What is the periodic trend for electron affinity (more negative) when moving down a group in the periodic table?

   Electron affinity becomes less negative down a group. Increased size weakens nuclear attraction, making electron addition less exothermic.

6. What is the periodic trend for first ionization energy when moving left to right across a period?

   First ionization energy increases across a period. Higher $Z_{\mathrm{eff}}$ and smaller radius make it harder to remove an electron.

7. What is the periodic trend for electronegativity when moving left to right across a period?

   Electronegativity increases across a period. Increasing $Z_{\mathrm{eff}}$ enhances attraction for shared electrons in bonds.

8. Which has the larger atomic radius: Na or Cl (both in period $3$)?

   Na has the larger atomic radius. Na experiences lower $Z_{\mathrm{eff}}$ than Cl due to position earlier in the period.

9. What is the periodic trend for first ionization energy when moving down a group in the periodic table?

   First ionization energy decreases down a group. Larger atomic radius reduces nuclear attraction on valence electrons, easing removal.

10. Which has the more negative electron affinity: Cl or Ar (same period $3$)?

    Cl has the more negative electron affinity. Cl, as a halogen, readily accepts an electron to complete octet, unlike noble gas Ar.

11. For an isoelectronic series, what is the trend in ionic radius as nuclear charge $Z$ increases?

    Ionic radius decreases as $Z$ increases (isoelectronic series). Higher nuclear charge compresses the same electron configuration more effectively.

12. What is the periodic trend for electronegativity when moving down a group in the periodic table?

    Electronegativity decreases down a group. Larger size diminishes nuclear pull on valence electrons, reducing attraction in bonds.

13. What is the periodic trend for metallic character when moving left to right across a period?

    Metallic character decreases across a period. Higher electronegativity and nonmetallic nature reduce tendency to lose electrons.

14. Which has the higher first ionization energy: Mg or Al (both in period $3$)?

    Mg has the higher first ionization energy. Mg's full 3s subshell is more stable than Al's 3p electron, requiring more energy to ionize.

15. What is the periodic trend for reactivity of alkali metals (group $1$) when moving down the group?

    Alkali metal reactivity increases down the group. Decreasing ionization energy down the group eases electron loss in reactions.

16. What is the periodic trend for atomic radius when moving down a group in the periodic table?

    Atomic radius increases down a group. Addition of new electron shells increases distance from nucleus, outweighing higher $Z_{\mathrm{eff}}$.

17. What is the relationship between $Z_{\mathrm{eff}}$ and atomic radius for atoms in the same period?

    Higher $Z_{\mathrm{eff}}$ corresponds to smaller atomic radius. Stronger nuclear pull contracts electron cloud in atoms with similar electron count.

18. What is the periodic trend for metallic character when moving down a group in the periodic table?

    Metallic character increases down a group. Lower ionization energy facilitates easier loss of electrons for metallic reactions.

19. Which has the larger atomic radius: K or Na (both in group $1$)?

    K has the larger atomic radius. K has an additional electron shell compared to Na, increasing overall size.

20. Which has the higher electronegativity: F or Cl (same group, different periods)?

    F has the higher electronegativity. Smaller size of F increases its ability to attract bonding electrons compared to Cl.

21. What happens to atomic radius when an atom forms a cation compared with the neutral atom?

    Radius decreases when a cation forms. Loss of electrons reduces electron-electron repulsion, allowing tighter nuclear pull.

22. What happens to atomic radius when an atom forms an anion compared with the neutral atom?

    Radius increases when an anion forms. Gain of electrons increases repulsion, expanding the electron cloud.

23. Which has the smallest radius in the isoelectronic set: O$^{2-}$, F$^-$, Ne, Na$^+$, Mg$^{2+}$?

    Mg$^{2+}$ has the smallest radius. Mg$^{2+}$ has the highest nuclear charge, pulling electrons closest in the series.

24. What is the effective nuclear charge $Z_{\mathrm{eff}}$ in terms of $Z$ and shielding $S$?

    $Z_{\mathrm{eff}}=Z-S$. Effective nuclear charge accounts for protons minus shielding by inner electrons.

25. Which has the higher first ionization energy: N or O (both in period $2$)?

    N has the higher first ionization energy. N's half-filled p subshell provides extra stability compared to O's paired electrons.

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