Here are the oxidation numbers of the requested elements in the given compounds: 1) Na2S - S has an oxidation number of -2 2) HClO4 - Cl has an oxidation number of +7 3) NaBrO3 - Br has an oxidation number of +5 4) NO3- - N has an oxidation number of +5 5) (NH4)2SO4 - S has an oxidation number of +6 6) CO32- - C has an oxidation number of +4 7) OF2 - O has an oxidation number of -1 8) H2O2 - O has an oxidation number of -1 9) CH3OH -

1. F
1.
2.
3.
4.
5.
6.
7.

2. (Zeff) F F F
F F F F F
F F Zeff
Element Al Si P S Cl Ar
Atomic# 13 14 15 16 17 18
Zeff 1+ 2+ 3+ 4+ 5+ 6+

3. F F FF F F (pm) (A )
1. F
F
F F
Cl-Cl = 198/2 = 99 pm
F C-Cl = 176 pm
Cl = 99 pm
C = (176-99) = 77 pm

4. 2. F F
F F
F F F
H2 H2
Kr Kr
F F Kr = 200 pm F F H = 120 pm

5. 3.
F F F
F F
Mg Mg
Mg = 320/2 = 160 pm
320 pm

6. Mg : 1s2 2s2 2p6 3s2
160 pm
F F
Mg2+ : 1s2 2s2 2p6
65 pm
O : 1s2 2s2 2p4
73 pm
O2- : 1s2 2s2 2p6
140 pm

7. F F F
F F
F
F
FF
F F F
F F
F F F F
F
F

8. F
F
“
F
F
”
“
”

9. Which is larger ?
1. Be2+ or B3+
2. Al3+ or P3-
3. K or Ca
4. As or Te
5. O2- or F-

10. Ionization energy
: F e- F
⇒ F e- ⇒ IE
⇒ F F e- F ⇒ IE

11. First Ionization Energy Plot
2500 He
Ne
First ionization energy (kJ/mol)
2000
F
Ar
1500 N Kr
Cl
H O Br
C P Zn As
1000 Be
Mg S Fe Ni Se
B Si Ca Ti Cr Co Cu Ge
Mn Sr
500 Al Sc V Ga
Li Na
K Rb
0
5 10 15 20 25 30 35 40
Atomic number

12. e- F F Nu F e- IE
First Ionization Energy
F First Ionization Energy
e- F
Nu
e- F
IE

13. Which member of each pair has the greater
first ionization energy? Why?
•Na or Na+
•F or Cl
•N or O
•O or F
•Na or Mg
•K or Na

14. Electron Affinity
Electron affinity (EA) F
F F
EA
F F
F EA F
F EA
X (g) + e- X-(g) FF F EA
F (g) + e- F-(g)
∆H = -328 kJ/mol EA = - 328 kJ/mol
O (g) + e- O-(g) ∆H = -141 kJ/mol EA = - 141 kJ/mol

15. Electron Affinity
F (g) + e- F-(g) ∆H = -328 kJ/mol EA = - 328 kJ/mol
F F F
F EA
O (g) + e- O-(g) EA = - 141 kJ/mol
O- (g) + e- O2-(g) EA = - 744 kJ/mol
1 F O- F EA2
F F -1 F F
F F F F F O2-

16. Electron Affinity
F F F F
F F
F e- F F e- F F F Nucleus F F
F F EA F
F F
F
F
F F
F
F F F F
F F
F F
F F EA F

17. F 2A F F F 1A
F 2A F subshell s F F
F F F shield F
F 1A F subshell s
F electron affinity F
* Li or Na
* O or F

18. Electronegativity
( Electronegativity ) F
FF Nucleus
e- F F F Nucleus
∴ EN
e- F F F F Nucleus F
∴ EN
FF
F F F F F F F F F
F F F F
F 4.0 ( Cs ) F F 0.7

19. Electronegativity
F EN F F F
F F EN
F F
EN
F
F F
F
F F
EN

20. . F F IA , IIA, IIIA
F
F
. F IA , IIA, IIIA F
F
F
F IVA VA F
F F F F
F IA IVA
F
( )

21. . F F VIA , VIIA, VIIIA
F F F F
. F VA, VIA , VIIA, VIIIA
F F
F F F F F
F VA VIIIA
F
( )

23. Oxidation Number
( Oxidation Number ) F
F F F
F
F
1. F FF F
F F F Na Be He O2 S8
2. F F F
Na+ F +1
Be2+ F +2
O2- F -2
3. ( F IA ) F F ( F IIA )
F F F +1 +2

24. Oxidation Number
4. F F F -2 F
F F F H2O2 Na2O2⇒ -1
F F F KO2 ⇒ -1/2
OF2 ⇒ +2
5. F F F +1 F
F F F -1 F
LiAlH4 NaBH4
6. F
F F F
KMnO4 F 0 NO3- F -1

25. Oxidation Number
F 1 S H2SO4
F 2 Co [Co(CN)6]4 -
S=x
Co = x
H = +1
CN- = -1
2 H = (+1 × 2) = +2
CN = (-1 × 6) = -6
O = -2
F
4 O = (-2 ×4) = -8
F -4
F 0
x + (-6) = -4
+2 + x + (-8) = 0
x = +2
x = +6
Co [Co(CN)6]4- = +2
S H2SO4 = +6

26. Oxidation Number

27. Oxidation Number
F F F F
1) Na2S 6) CO32-
2) HClO4 7) OF2
3) NaBrO3 8) H2O2
4) NO3- 9) CH3OH
5) (NH4)2SO4 10) S8
Find the oxidation number of sulphur in the following compounds-
SO4 2-, S2O32-, H2S2O7, S4O62-, SO32-
Find the oxidation number of the metal in the following complexes-
AlF63-, KClO2, KHSO4, CrF63-, AlCl3