Classify below into more useful and less useful minerals in our food: iron, calcium, magnesium, chloride, selenium, potassium, phosphorous,  zinc, iodine, mercury, copper. 
 In the given minerals, these are the minerals more useful to have in our foods: magnesium, sodium, calcium, phosphorous, chloride and potassium.
In the given minerals, these are the minerals less useful to have in our foods: iron, iodine, zinc, selenium, copper and mercury