Chemical and healthy water components

(1) According to the contents of the mineral water label and the expression method of ions: in the upper right corner of the element symbol representing ions, mark the number of positive and negative charges carried by ions, with the number in front and the positive and negative symbols behind. If there are 1 charges, 1 should be omitted. If there are multiple ions, add the corresponding number before the element symbol; Therefore, a cation is expressed as: Mg2+, k+; Anions are expressed as: Cl-;

So the answer is: Mg2+, k+; cl-；

(2) According to the expression method of element valence: determine the valence of the element to be labeled in the compound, and then use the symbol and number above the element in its chemical formula, with the symbol in front and the number behind, so the valence of oxygen in water is expressed as: H2? 2O； ? According to the number in the lower right corner of the element symbol in the chemical formula, the number of atoms in the molecule is indicated; The meaning of 2 in H2O is as follows: there are two hydrogen atoms in a water molecule;

So the answer is: H2? 2O； There are two hydrogen atoms in a water molecule;

(3) Fish can breathe in water, providing oxygen for breathing, which is shown as O2; So the answer is: O2;

(4) According to the writing steps of the chemical formula of the compound: classification → sequencing → pricing → crossover → reduction, so the chemical formula of magnesium sulfate is: MgSO4；;

So the answer is: mgso 4.