Why did mendeleev leave empty spaces in his periodic table?

Why did southern business leaders want to increase the number of slaves

What shape would a molecule with two bound groups and two lone pairs have?

Ican determine the molar mass of an element by looking on the under the atomic mass for the element. for example the molar mass of phosphorus is 30.974 grams/mole. avogadro’s number tells me the amount of representative particles in 1 mole of any substance. this means 12.011 gram sample of carbon and a 32.0 gram sample of sulfur have the same number of atoms.