The electron configuration of an element is 1s22s2. How many valence electrons does the element have?

How has the scientific community addressed the safety of chemicals? a. chemicals are repeatedly tested, even those that have existed for a long time. b. existing chemicals are tested if they have never been tested before. c. chemicals are tested if they are suspected to have caused a problem. d. only new chemicals are tested.

Match each statement with the state of matter it describes

In an exothermic reaction at equilibrium, what is the effect of lowering the temperature? a. the reaction makes more products. b. the reaction makes more reactants. c. the reaction is unchanged.