Plleeeaaassee !

how many protons, neutrons, and electrons does rubidium-87 contain? *

a) 87 protons, 85.5 neutrons, 87 electrons
b) 37 protons, 37 neutrons, 37 electrons
c) 37 protons, 87 neutrons, 37 electrons
d) 37 protons, 40 neutrons, 37 electrons

Ageologist determines that a sample of a mineral can't be scratched by a steel nail but can be scratched by a masonry drill bit. based on this information, the sample mineral has to be softer than a. orthoclase. b. fluorite. c. apatite. d. corundum.

Which diagram represents the phase tha occurs after a solid melts?

Magnesium is the limiting reactant in this experiment. calculate the theoretical yield of mgo for each trial. trial 1: trial 2: data mass of empty crucible with lid trial 1: 26.688 trial 2: 26.681 mass of mg metal, crucible, and lid trial 1: 26.994 trial: 2 26.985 mass of mgo, crucible, and lid trial 1: 27.188 trial 2: 27.180