What observations by Rutherford led to the hypothesis that atoms are mostly empty space, and that almost all of the mass of
the atom is contained in an atomic nucleus?

Answerhund's rule;

Answer the molar mass of magnesium is 24.305g/mol.

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.