In the form of what compounds do the metals potassium, magnesium chromium and zinc occur

In the form of what compounds do the metals potassium, magnesium chromium and zinc occur in nature? Write down the chemical formulas for these compounds.

1. In a free state, potassium is not found in nature. In the composition of minerals, potassium is present in sylvite KCl, sylvinite nNaCl + mKCl, carnallite KCl · MgCl2 · 6H2O. It is also present in plant ash as K2CO3 carbonate.

2. Magnesium is a common element of the earth’s crust. It does not occur in a free state in nature. It is part of sea water. It is a part of many minerals, for example, olivine (Mg, Fe) 2 [SiO4], dolomite CaMg [CO3] 2, bischofite MgCl2 · 6H2O, magnesite MgCO3.

3. Chromium is a fairly common element in the earth’s crust. Present in seawater. The main chromium compounds: chromite FeCr2O4, crocoite PbCrO4.

4. Zinc is not found in its pure form in nature, but it is present in the earth’s crust, in sea water. There are 66 known zinc minerals, including sphalerite (or zinc blende) ZnS, zincite ZnO, smithsonite ZnCO3.