If the valency of calcium is $2$, derive the valencies of the other elements or radicals present in the following compounds: Calcium chloride $\left({\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{l}}_2\right)$, Calcium hydroxide $\left(\mathrm{C}\mathrm{a}{\left(\mathrm{O}\mathrm{H}\right)}_2\right)$, Calcium phosphate $\left({\mathrm{C}\mathrm{a}}_3{\left(\mathrm{P}{\mathrm{O}}_4\right)}_2\right)$.

Solve the crossword puzzle.

Across

4. Basic particles of matter

6. Atomicity of oxygen

7. Consists of only one type of atom

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1. He was the first one to use picture symbols to denote elements

2. Can be separated into constituents by simple physical methods 

3. Molecules with positive or negative charges

5. The supporter of inflammable gas.

Using the definitions, decide whether the following diagram represents an element, a compound, or a mixture. Explain your choice.

Using the definitions, decide whether the following diagram represents an element, a compound, or a mixture. Explain your choice.

Using the definitions, decide whether the following diagram represents an element, a compound, or a mixture. Explain your choice.