What type or tectonic plate boundary is associated with tension stress

When the earth was formed and cooled, why did nickel and iron end up in the center of the earth while basalt and granite ended up in the outer layers

Elements in group 2 are all called alkaline earth metals. what is most similar about the alkaline earth metals?

A2.5% (by mass) solution concentration signifies that there is a 2.5 % (by mass) solution concentration signifies that there is blank of solute in every 100 g of solution. of solute in every 100 g of solution