Which of the following atoms has an electric charge? a sodium atom with 11 protons, 11 electrons, and 12 neutrons
a calcium atom with 20 protons, 18 electrons, and 20 neutrons
a helium atom with 2 protons, 2 electrons, and 2 neutrons
an iron atom with 26 protons, 26 electrons, and 30 neutrons

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

Ten students stand in a circle and are told to make a transverse wave. what best describes the motion of the students? each student bumps the shoulder of his or her neighbor. at the exact time, all students take a step to the right. the students skip clockwise, going in a circular motion. one at a time, each student lifts his or her hands up and then down.

Like a key in a lock, the shape of the. must bind with the. of the recieving neuron