Which of these relationships is true of an uncharged atom? A) The atomic mass is equal to the atomic number.
B) The number of electrons is equal to the number of neutrons.
C) The number of protons is equal to the number of electrons.
D) The atomic mass is equal to the number of electrons.

The correct option is  C) The number of protons is equal to the number of electrons.

Explanation:

Atoms are made up of particles called protons, neutrons, and electrons. Protons and neutrons are in the center of the atom and form the nucleus, while electrons surround the nucleus. Electrons have a negative charge. The charge of the protons is positive and finally, the neutrons have no charge.

If the atom has no charge, this means that the total charge of the atomic nucleus, which is positive due to the presence of the protons, is equal to the negative charge of the electrons, so that it cancels out.

So, the correct option is  C) The number of protons is equal to the number of electrons.

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