Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons? a. the proton's negative charge holds electrons in the atom. b. the nucleus doesn't change in stable isotopes. c. protons at the atom's surface determine the atom's behavior. d. 99% of the atom's mass consists of protons. e. none of these. elements are defined by the number of protons.

Copper has free electrons per cubic meter. a 71.0-cm length of 12-gauge copper wire that is 2.05 mm in diameter carries 4.85 a of current. (a) how much time does it take for an electron to travel the length of the wire? (b) repeat part (a) for 6-gauge copper wire (diameter 4.12 mm) of the same length that carries the same current. (c) generally speaking, how does changing the diameter of a wire that carries a given amount of current affect the drift velocity of the electrons in the wire?

*drag each tile to the correct location in the sequence* the table shows chronological events in the life of our sun, a medium-sized star. place the missing events into the correct rows of the table.

Could someone me find the answer to this problem.