A scientist studying stars can estimate the temperatures of stars by their?

Is this a single replacement reaction or there is no

Me i dont know what to do! the table compares the number of electrons in two unknown neutral atoms. comparison of electrons atom number of electrons a 10 d 11 use this information to determine the number of valence electrons in the atoms. which of the following correctly compares the stability of the two atoms? both are unreactive. both are highly reactive. a is unreactive and d is reactive. a is reactive and d is unreactive.

From the options provided for each element below, choose the properties that it may have based on its location in the periodic table fluorine (f): highly reactive nonmetal shiny a conductor