How many dots should be shown in the Lewis dot diagram of oxygen?

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

In the reaction between a crushed antacid tablet and vinegar what gas is emitted

An atom of which element reacts with an atom of hydrogen to form a bond with the greatest degree of polarity ?