You have three gases in a mixture where P1 = 150 kPa, P2 = 75 kPa, and P3 = 100 kPa. What is the total pressure of the gas mixture? * 325 kPa
225 kPa
175 kPa
250 kPa

The mass of an atom comes from the protons and neutrons that are found in the nucleus. The number of protons is the atomic number of an element. To find the number of neutrons, subtract the atomic number from the mass of an atom. So, if an atom is missing a neutron or has an extra neutron, the atom is called an isotope. An atom is still the same element if it is missing an electron. That is also true for isotopes. They are the same element but their number of neutron differs.