What is the name of the element hydrogen
helium
lithium
beryllium
boron
carbon
nitrogen
oxygen
fluorine
neon

Compare and contrast physical changes with chemical changes.

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?

At 20°c, a sample of h2o liquid and a sample of co2 gas each have the same average kinetic energy. why is one a liquid and the other a gas at this temperature?