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Please see below solution:
1 lb Hg x (151.50/76 lb) = cost of 1 lb. 
<span>cost 1 lb x (1g/453.6 g) = cost of 1 g.</span>
        
                    
             
        
        
        
7. 1,2,2,2
8. 4,3,1
9. 1,4,1,2
10. 3,4,1,4
        
             
        
        
        
Answer:
2+
Explanation:
The charge on Z in the compound ZB₂ is a 2+   
   From the given compound: 
    We know that Br is bromine with a charge of -1;
 So; 
    Using the combining power approach: 
Atoms                              Z                                Br
Combining power           2                                1 
Exchange of valency      1                                 2 
 So; 
   The charge on Z is  2+
           2
 
        
             
        
        
        
The fourth period contains 18 elements, beginning with potassium and ending with krypton. As a rule, period 4 elements fill their 4s shells first, then their 3d and 4p shells, in that order; however, there are exceptions, such as chromium.
Cr. I think