Atoms and the Periodic Table

3. the tiny extremely dense, positively charged region in the center of an atom; made up of protons and neutrons
4. a column of elements on the periodic table
5. a pure substance composed of two or more elements that are chemically combined
6. the element in Group 2 of the periodic table; they are reactive than alkali metals; there atoms have to electrons in their outer level
12. the number of protons in the nucleus of an atom
14. the particles of the nucleus that have no charge
15. elements that are dull and are poor conductors of thermal energy and electric current
16. the weighted average of the masses of all the naturally occurring isotopes of an element
17. elements in Group 1 of the periodic table;they are the most reactive metals;their atoms have one electron in there outer level
19. the positively charged particles of the nucleus; the number of protons in a nucleus is the atomic number that determines the identity of an element

1. the law that states that the chemical and physical properties of elements are perodic functions of their atomic number
2. the sum of the protons and neutrons in an atom
7. atoms that have the same number of protons but have different number of neutrons
8. a pure substance that can't be separated or broken down into simpler substances by physical or chemical
9. the regions inside an atom where electrons are likely to be found
10. smallest particle into which an element can be divided and still be the same substance
11. elements that are shiny and are good conductors of thermal energy and electric current; most metals are malleable and ductile
13. elements that have properties of both metals and nonmetals;sometimes referred to as semiconductors
18. the negatively charged particles found in all atoms; electrons are involved in the formation of chemical bonds
19. a horizontal row of elements on the periodic table