What must models and theories do in order to remain valid

What is the mass in kilograms of 1.20x 1028 atoms of copper, cu?

Nonmetals tend to form what kind of ions?

I am on the 2th period and belong to the same group as silicon who am I?

What mass of silver ag which has an atomic mass of 107.87 amu contains the same number of atoms contained in 10.0g of boron b which has an atomic mass of 10.81 amu?

Helium (he) has an atomic number of 2. it is chemically stable because it

What is the name of the compound Sr3N2?

The water softener discussed here relies on precipitation softening also known as ion exchange. based o hte reactants used, what ions would remain in the softened water thaat would be consumed buy the homeowners

What would be the best technique to separate a soluble solid from a solution, like separating salt from a mixture of salt water?

What are metalloids used for

Which scientist developed the quantum mechanical model of the atom? a. Albert Einstein c. Niels Bohr b. Erwin Schrodinger d. Ernest Rutherford