What is the new concentration of solution if 25mL added to 125ml of .150

The number to the right of an element's symbol (ex. c-12) identifies the of an isotope.

Which of the following units is not an official si unit

With the largest atoms and the smallest number of valence electrons and with the smallest atoms and the greatest number of valence electrons are the most reactive. a. nonmetals; metals b. nonmetals; transition elements c. transition elements; metals d. metals; nonmetals