True or false: An element has two layers of electrons. The electrons in the outermost layer are called distance electrons. and how many layers

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. she has foam balls for the protons, neutrons, and electrons. she has added 6 neutrons to her model so far. how many more neutrons does she need to add to complete her neutral atom of magnesium?

A50.0g sample of liquid water at 0.0 c ends up as ice at -20.0 c. how much energy is involved in this change?

At which temperature would a reaction with ah= -220 kj/mol and as=-0.05 kj/(mol-k) be spontaneous?