SCHEDULE CHANGE. A planned change or a flight number/time change which can occur up to more than 72 hours prior to the flight's scheduled. departure. Examples - Change of flight times, change of flight numbers, reduction of service, discontinuation of all service. in a market. American uses an automated schedule change process up to 72 hours prior to departure. Through this automated. process all schedule changes are sent to the booking source for notification.
Describe the particles that make up the nucleus of an atom in terms of mass and charge. Protons, neutrons and electrons. Protons have a relative mass of 1 and a charge of +1, they are found in the nucleus of an atom.
The total number of nucleons - protons and neutrons - in the nucleus of an atom is called the Mass Number. For example, the most common isotope of fluorine has an atomic number of 9 and a mass number of 19. The atomic number tells us there are 9 protons in the nucleus (and also 9 electrons in the shells surrounding the nucleus). The mass number tells us the nucleus contains 19 particles in total. Since 9 of these are protons, the other 10 are neutrons. We call it the mass number because virtually all the mass in an atom comes from the protons and neutrons - electrons weigh about 1/2000th of the mass of a proton or neutron.