What is the purpose of mixing salt with the ice in a homemade ice cream maker?

The number to the right of an element's symbol (ex. c-12) identifies the of an isotope.

When the mercury level in a barometer decreases that atmospheric pressure has

In chemistry, the type of an atom (what element it is) is determined by: a) the number of protons it contains in its nucleus.b) the number of neutrons it contains in its nucleus.c) the number of protons it has in a cloud around the nucleus.d) the number of neutrons it has in a cloud around the nucleus.e) the number of electrons it exchanges with its neighbors.