Questions (40 blanks)

1. The modern periodic law was proposed by ________ in the year ________.
2. In the modern periodic law, properties of elements are periodic functions of their ________.
3. The long form of the periodic table has ________ periods and ________ groups.
4. s-block elements have the outer configuration ________ (Group 1) and ________ (Group 2).
5. p-block elements have the outer configuration ________.
6. d-block elements have the outer configuration ________.
7. f-block elements have the outer configuration ________.
8. Atomic radius ________ across a period due to ________ Zeff.
9. Atomic radius ________ down a group because ________.
10. Cations are ________ than their parent atoms; anions are ________ than their parent atoms.
11. For isoelectronic species, radius decreases as ________ increases.
12. $IE_{1}$ of Be (________ kJ/mol) is greater than $IE_{1}$ of B (________ kJ/mol).
13. The reason IE(Be) > IE(B) is that Be loses an electron from the ________ subshell while B loses from ________.
14. IE of N (________ kJ/mol) is greater than IE of O (________ kJ/mol) because N has a ________ 2$p^{3}$ configuration.
15. The electron gain enthalpy of chlorine is ________ kJ/mol.
16. The electron gain enthalpy of fluorine is ________ kJ/mol.
17. The element with the most negative EGE among halogens is ________.
18. Fluorine's EGE is less negative than chlorine's because of ________ in F's compact ________ orbital.
19. Electronegativity of fluorine on the Pauling scale is ________.
20. Electronegativity ________ across a period and ________ down a group.
21. The three diagonal relationship pairs are ________, ________, and ________.
22. Diagonal relationships arise due to similar ________ ratios.
23. Both Be and Al oxides are ________ — they dissolve in both acids and ________.
24. Both B and Si chlorides are hydrolyzed by water, producing ________ and ________ respectively.
25. Noble gases have ________ (positive/negative) EGE.
26. Groups ________ and ________ show less negative EGE due to filled/half-filled subshell stability.
27. The isoelectronic 10-electron series in decreasing radius order: ________ > ________ > ________ > ________ > ________ > ________.
28. The ionic radius of $O^{2-}$ is ________ pm; $F^{-}$ is ________ pm; $Na^{+}$ is ________ pm; $Mg^{2+}$ is ________ pm.
29. He is placed in Group ________ despite having an $ns^{2}$ configuration similar to Group 2.
30. Cu has the configuration ________ (not 3$d^{9}$ 4$s^{2}$) due to extra stability of ________.
31. Cr has the configuration ________ due to extra stability of ________.
32. Period number of an element = ________.
33. First element of each group shows anomalous behavior due to small size, high EN, and absence of ________.
34. Zeff = Z − ________.
35. Ionization enthalpy is always ________ (endothermic/exothermic).
36. For most non-metals, electron gain enthalpy is ________ (endothermic/exothermic).
37. Diagonal element to Li is ________, and diagonal element to Be is ________.
38. The block classification depends on which ________ the last electron enters.
39. In the second period, the two exceptions to the general IE trend occur between ________ and ________, and between ________ and ________.
40. Lanthanoid contraction occurs due to poor shielding by ________ electrons.