an atom's mass comes from protons and neutrons.
where does an atom's mass come from?
protons and neutrons
section::::properties.:mass.









































the large majority of an atom's mass comes from the protons and neutrons that make it up. the total number of these particles (called "nucleons") in a given atom is called the mass number. it is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. an example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons).
atom
the 2nd mass learn of militias fighting against the espheni worldwide with the help of the volm, who also inform them that the espheni are active in several capital cities around the world, and have placed jamming signals to prevent them from learning exactly what they're doing. they come to learn that the final battle against the espheni could be in washington d.c. and they begin a slow march towards the city. along the way tom learns that the dornians were the first race the espheni destroyed, and the skitters that they've been fighting were once dornians until the espheni transformed them into their servants. pope and sara begin a romance that is short-lived when she is stuck and killed in an espheni trap; pope blames tom for her death when he chose to destroy a facility that was mass-producing skitters instead of saving her. tom, sick of pope's constant complaining and vitriol, kicks him out of the 2nd mass; several others including anthony go with him. the 2nd mass come across a naval station currently occupied by a group of soldiers under the command of female captain named katie marshall with whom weaver once had a relationship. tom and his sons are imprisoned for conspiring with the espheni; anne is eventually arrested as well once the soldiers learn that her daughter was half-espheni. weaver becomes suspicious of katie's behavior, noting that she's not acting like her normal self (to which other soldiers agree); he follows her off-base one night and finds her talking to an overlord which he then kills after she leaves. katie, under the orders of the overlord, tries and convicts tom and his family of aiding the enemy and orders their execution. weaver, along with other soldiers convinced that captain marshall isn't herself, refuse to carry out the execution. when katie tries to shoot them herself, weaver fatally stabs her. katie dies shortly afterward, confessing that she wasn't the real katie but an espheni doppelganger sent to infiltrate human resistance groups.
falling skies (season 5)