What are the two key concepts for this section? What is matter? Distinguish between an element and a compound and give an example of each. What is the periodic table of elements? Define atom,...

What are the two key concepts for this section? What is matter? Distinguish between an element and a compound and give an example of each. What is the periodic table of elements? Define atom, molecule, and ion and give an example of each. What is the atomic theory? Distinguish among protons, neutrons, and electrons. What is the nucleus of an atom? Distinguish between the atomic number and the mass number of an element. What are isotopes? What is acidity? What is pH? Define chemical formula and give two examples.