U-238, the common isotope of uranium, has 92 protons, 146 neutrons, and 92 electrons. U-235 is another isotope of uranium. How do the number of subatomic particles of U-238 and U-235 differ?

A. U-238 has three more electrons than U-235.
B. U-238 has three more neutrons than U-235.
C. U-238 has one more proton and two more neutrons than U-235.
D. U-238 has one more electron and two more protons than U-235.

How are mixtures different from compounds?

A. Mixtures combine to produce salts; compounds do not.
B. Mixtures can be separated by physical means; compounds cannot.
C. Mixtures combine several different elements; compounds only combine one element.
D. Mixtures involve particles that can be seen, like sand; compounds involve particles that cannot be seen, like air.

1) Comparison of U-238 and U-235

Isotopes are atoms of the same element that differ in the number of neutron. Different isotopes of the same element have the same number of protons and electrons.

The difference between U-238 and U-235 is that U-238 has 146 neutrons (146 neutrons + 92 protons = 238 number of mass), while U-235 has 143 neutrons (143 neutrons + 92 protons = 235 number of mass).

Therefore, the answer is the option b. U-238 has 3 more neutrons than U-235.

2) How are mixtures different from compounds?

The answer is the option B. Mixtures can be separated by physical means; compounds cannot.

The compounds have a defined composition so they cannot be separated into their elements by physical means. The mixtures combine different compunds which can be separated by evaporation, distilation, or many other physical means.