How many valence electrons would be shown in the electron dot diagram of a helium atom?

Working with si (metric) units for each of the following commonly used measurements, indicate its symbol. liter gram milliliter kilogram meter centigram milligram centimeter kilometer second millimeter milliseconds

According to the diagram; a) identify the anode of the cell and write the half-reaction that occurs there b) write the overall equation for the reaction that occurs as the cell operates c) calculate the value of the standard cell potential ,e cell. d)write the shorthand notation of the cell above e)indicate the flow of the electrons on the diagram

Why does his teacher ask him to balance the equation by including the correct coefficient