Which two elements have the same number of valence electrons?

Na and Sr
Zr and H
O and S
Mg and P

Aglow stick contains a glass vial with chemicals. when the glow stick is bent, the vial breaks and the chemicals react to produce a glow. a science student observes that a glow stick kept in the freezer glows for a longer duration than a glow stick kept at room temperature. what conclusion can be drawn based on the observation? be sure to note the outcome and test variables in the conclusion.

How many moles of bromine are needed to produce 3.23 moles of potassium bromide

What type of context clue you understand the meaning of  quandary?