CHapter 19

1. particles of matter that make up protons and neutrons
5. particle, composed of quarks, inside the nucleus of an atom that has a positive charge
6. the smallest particle of an element that still retains the properties of the element
8. uses the symbol for an element and dots representing the number of electrons in an element's outer energy level
9. horizontal row in the periodic table
12. sum of the number of protons and neutrons in an atom's nucleus
14. positively charged center of an atom that contains protons and neutrons and is surrounded by a cloud of electrons

2. weighted-average mass of the mixture of an element's isotopes
3. number of proton in an atom's nucleus
4. particles surrounding the center of an atom that have a negative charge
7. organized list of all known elements that are arranged by increasing atomic number and by changes in chemical and physical properties
8. area around the nucleus of an atom where the atom's electrons are most likely to be found
10. atoms of the same element that have different number of neutrons
11. vertical column in the periodic table
13. neutral particle, composed of quarks, inside the nucleus of an atom