**Part B**. A certain metal hydroxide, M(OH)_{2}, contains 32.8% oxygen by mass. What is the identity of the metal M?

Percent composition refers to the mass percent of each element in a compound:

$\mathbf{mass}\mathbf{}\mathbf{percent}\mathbf{=}\frac{\mathbf{mass}\mathbf{}\mathbf{of}\mathbf{}\mathbf{element}}{\mathbf{mass}\mathbf{}\mathbf{of}\mathbf{}\mathbf{compound}}\mathbf{\times}\mathbf{100}\mathbf{\%}$

For example, the percent composition of water, H2O, is 11.2% hydrogen and 88.8% oxygen. Therefore, a 100-g sample of water contains 11.2 g of hydrogen atoms and 88.8 g of oxygen atoms.

The periodic table will be useful when doing this problem. You can access a periodic table by clicking the "Tools" link in the upper right corner of this page.

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