8. Aln Aluminum
   Write the formulas of the following i
9. potassium iodide
10. magnesium oxide
11. aluminum chloride
12. sodium nitrate
13. calcium carbonate

Potassium iodide is represented by the formula KI, where potassium (K) is in Group 1 of the periodic table and forms a 1+ ion, while iodine (I) forms a 1- ion. Together, they create a stable ionic compound that’s commonly used in medical applications and as a nutritional supplement to prevent iodine deficiency.

Magnesium oxide has the chemical formula MgO. Magnesium (Mg) is in Group 2 and forms a 2+ ion, while oxygen (O) forms a 2- ion. This compound is notable for its high melting point and is often used as a refractory material in furnace linings and in various chemical applications, including as a dietary supplement for magnesium.

Aluminum chloride is represented as AlCl₃, where aluminum (Al) which forms a 3+ ion combines with three chloride (Cl) ions, each with a 1- charge. This compound is a key player in the Lewis acid chemistry and is used in the production of aluminum metal and in various applications like water purification.

Sodium nitrate is formulated as NaNO₃, consisting of sodium ions (Na), which have a 1+ charge, paired with the nitrate ion (NO₃), which carries a 1- charge. This compound is widely utilized in fertilizers and food preservation because of its nitrogen content, boosting plant growth and enhancing flavor.

Calcium carbonate has the formula CaCO₃, where calcium (Ca) carries a 2+ charge and pairs with the carbonate ion (CO₃) which has a 2- charge. This versatile compound is found in rocks and minerals, and it is popularly used in construction, as a dietary calcium supplement, and in antacid tablets to relieve indigestion.