Unit 5

1. reduce the amount of activation energy that is needed for a reaction to take place
5. the simplest particle of an element
8. one or more substances change to produce on or more different substances
10. is anything that occupies space and has mass
11. the ability to do work
12. central region, makes up the bulk of the mass
14. when two atoms share one or more pairs of electrons
17. are attractive forces that hold atoms together
20. proceed in only one direction

2. number of protons
3. is a three dimensional region around a nucleus that indicates that probable location of an electron
4. sodium ion and chloride ion attract each other
6. is the simplest part of a substance the retains all of the properties
7. the amount of energy needed to start the reaction
9. made up of atoms of two or more elements in fixed proportions
10. an atom is equal to the total number of protons an neutrons of an atom
13. negatively charged particles
15. are substances that cannot be broken down chemically into simpler kinds of matter
16. atoms of the same element that have a different number of neutrons
18. an atom or molecule with an electrical charge
19. is the quantity of matter an object has