The periodic table crossword

2. Principle / electrons fills up from the lowest orbital
4. / horizontal rows in the periodic table
6. mass / average mass of the atoms in the nucleus
8. / smallest part of an element
9. configuration / The arrangement of electrons in an atom
12. earth metals / element that is on group 2 on the periodic table
13. / nonmetallic element on group 17
15. mixture / mixture that can see the elements
17. number / integer that equals to the number of protons and neutrons
18. / elements that doesn't have any properties of a metal
19. / substance that is made with 2 or more elements chemically bonded together
21. rule / every orbital in a sub-shell is singly occupied with one electron before any one orbital is doubly occupied

1. electron / outer shell electron that can be used for transferring or sharing with another atom
3. / vertical columns in the periodic table
5. / element that can conduct electricity and heat
7. / elements that have properties of both metals and nonmetals
10. / substance that is made with one atom
11. / contains both protons and neutrons
14. gases / element on group 18 that have a very low reactivity
15. mixture / mixture that cannot be separated by elements
16. / positive charged particle
20. exclusion Principle / orbitals have only 2 electrons that have opposite spins