Question

1. what is a polyatomic ions? give deux examples
2. where are the polyatomic ions usually found in the period table?
3. what is an oxoanion? give an example
4. how to write a formula with a polyatomic ions? give an example

Explanation:

1. Polyatomic ions are ions composed of two or more atoms covalently bonded together, acting as a single unit with an overall charge. Examples: $\text{NO}_3^-$ (nitrate ion), $\text{SO}_4^{2-}$ (sulfate ion).
2. Polyatomic ions are not found in a specific location in the periodic table as they are combinations of different elements. However, the elements that form polyatomic ions are mainly non - metals (e.g., N, O, S, etc.) which are located on the right side of the periodic table.
3. An oxoanion is a polyatomic anion that contains oxygen. Example: $\text{CO}_3^{2 -}$ (carbonate ion).
4. To write a formula with a polyatomic ion:

• Determine the charge of the polyatomic ion and the other ion (cation or anion).
• Use the criss - cross method (if applicable). For example, for sodium nitrate ($\text{NaNO}_3$):
• Sodium ion ($\text{Na}^+$) has a charge of + 1, nitrate ion ($\text{NO}_3^-$) has a charge of - 1.
• The formula is written by balancing the charges.

Answer:

1. Polyatomic ions are ions composed of two or more atoms covalently bonded together, acting as a single unit with an overall charge. Examples: $\text{NO}_3^-$, $\text{SO}_4^{2-}$.
2. Polyatomic ions are not found in a specific location in the periodic table. The elements that form them (mainly non - metals) are on the right side.
3. An oxoanion is a polyatomic anion that contains oxygen. Example: $\text{CO}_3^{2 -}$.
4. To write a formula with a polyatomic ion: Determine the charges and use the criss - cross method (if applicable). Example: $\text{NaNO}_3$.