An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom?

How do you identify the anode on a power source such as a battery? how do you identify the cathode? how are terms anion and cation?

Astring vibrates with a frequency of 10 hz. why can't a person hear the sound waves produced by the vibrating string, no matter how large the amplitude of the waves? out! this is homework and due tomorrow! you so much!

I’m an electrically neutral atomic any element, there are equal numbers of