This is a homogenous mixture because you cannot differentiate between the members of the mixture. A technique might be heating them until one melts and evaporates due to different boiling temperatures, or mixing them together with fluids that would dissolve one, yet keep the other one whole.
The alkaline earth metals (the second group) because their ion charge is +2
When you are looking in a jewelry store and you want to know how many carrots are in the diamonds.
Coal is not a mineral. It's not a mineral because minerals are inorganic. Coal is organic because it comes from decayed living matter.
