Which of the following forms cations that can have different charges? 

a. lead 

b. cobalt 

c. Cr 

d. Ce 

e. all of the above

Which among the following elements does not exist as a diatomic molecule in nature? 

a. hydrogen 

b. nitrogen 

c. fluorine 

d. neon 

e. none of these 

What is the charge on the radium ion? 

a. 1+ 

b. 2+ 

c. 3+ 

d. 1- 

e. 2-

What is the correct formula of a compound that contains three sulfide ions and two aluminum ions? 

a. S₃Al₂ 

b. S₂Al₃ 

c. Al₂S₃ 

d. Al₃S₂ 

e. none of the above