What is the difference between copernicus's and kepler's description of planetary orbits

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.

Which characteristics can be used to differentiate star systems? check all that apply.

When hydrogen peroxide (h2o2) is added to potassium iodide (ki) solution, the hydrogen peroxide decomposes into water (h2o) and oxygen (o2). the chemical equation for the decomposition reaction is: 2h2o2—> 2h2o + o2. what is the role of the potassium iodide in this reaction? a. reactant. b. product. c. precipitate. d. catalyst.