Explain how experimental evidence led scientists to suggest the
nuclear model of the atom,

In 1909 Ernest Rutherford designed an experiment to test the plum pudding model. In the experiment, positively charged alpha particles were fired at thin gold foil. Most alpha particles went straight through the foil. This evidence led Rutherford to suggest a new model for the atom, called the nuclear model

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.