Question

1. What common feature exists in the electronic structure of elements in group 2 (the alkaline earth metals)? How about group 6 (the chalcogens)?

2. Notice how Mendeleev correctly predicted the formulas for the oxides and chlorides of the elements shown in Figure 8.1 on page 339 in the Tro textbook. Using these examples as a guide, suggest the formula for the oxide of a group 2 element? For group 6, what would be the common formula for the chloride?

3. When Mendeleev first discovered the periodic table, the noble gasses where not known. How did this discovery alter the periodic table and what key quantum concept does this emphasize?

4. Find the formulas for the anhydride of each of the following molecules. To obtain the formula of an anhydride, subtract H2O units from the formula until all hydrogens have been subtracted. If the molecule has an odd number of hydrogens, double its formula first.

a. H2SO4

EXAMPLE: Subtracting one H2O unit from H2SO4 leaves SO3. This is the anhydride formula for this acid. Follow this procedure for the remaining compounds below:

b. NaOH

c. HClO4

d. H3PO4

e. Ca(OH)2

f. H2CO3

g. HNO3

5. Determine the formula of the parent acid of each of the following anhydrides. To find the formula of the acid, add the indicated number of water molecules to the formula. Finally, divide through if the formula is divisible by some common factor.

a. SO2 (1 H2O) _______________________

b. N2O5 (1 H2O) _______________________

c. CO2 (1 H2O) _______________________

d. P4O10 (6 H2O) _______________________

6. Halogens and halides.

a. Draw Lewis dot structures for each of the halogen molecules, F2, Cl2, Br2, and I2.

b. Based on the periodic trends, which of the halogen molecules do you expect to have the shortest bond? Why?

c. Based on periodic trends, which halide ion, X¯, will be most stable, that is, lowest in energy? Briefly explain your reasoning.

Answer 1

Ans 1 :

The electronic structure of s and p block elements correspond to the group number of these elements.

So if the element lies in group 2 (alkaline earth metals) , it indicates that there are 2 valence electrons in its outermost shell , such that its general electron configuration will be ns² , where n is the number of outermost shell ( principla quantum number).

Likewise the elements in group 6 (chalcogens) , have 6 electrons in their valence shell , so that the general electron configuration of the elements become : ns² np⁴.