Aparticular atom of calcium has 20 protons, 21 neutrons, and 19 electrons. what is the electrical charge on this atom?

An animal cell loses the ability to convert energy stored in food to energy that the cell can use. which of the cell's organelles has stopped working? a. the mitochondria b. the nucleus c. the vacuoles d. the endoplasmic reticulum

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the independent variable in galileo's experiment? a. the speed of the ball b. the slope of the plane c. whether the ball moved d. what the ball was made of

Which of the following is a conclusion that resulted from ernest rutherford’s scattering experiment? (will mark brainliest) a. the nucleus is negatively charged b. the atom is a dense solid and is indivisible c. the mass is conserved when atoms react chemically d. the nucleus is very small and the atom is mostly empty space