Chemistry Vocab Test 1

4. A number in front of a chemical formula that shows how many molecules or atoms are present
7. the area surrounding the nucleus of an atom; where the electrons are found
10. the mass of an atom, approximately equal to the number of protons and neutrons in the atom
12. a group of atoms bonded together forming the smallest fundamental unit of a pure substance
13. A substance produced in a chemical reaction
15. A positively charged particle found the nucleus and makes up half of the mass of an atom.
16. A neutrally charged particle found the nucleus and makes up half of the mass of an atom.
17. the basic unit of an element and makes up everything
19. A combination of symbols that represent the elements in a compound

1. A chemical substance that is present at the start of a chemical reaction
2. A negatively charged particle found the electron cloud and has very little mass
3. the number of protons in the nucleus of a single atom
5. The electrons in the outermost energy level of an atom that influence the reactivity of the element
6. The tiny, very dense, positively charged region in the center of an atom; made up of protons and neutrons
8. A pure substance made of only one kind of atom and cannot be broken down
9. A substance made up of atoms of two or more different elements joined by chemical bonds
11. A number written to the bottom right of a chemical symbol that shows how many atoms of that element are in a compound.
13. The rows in a Periodic Table that classify the elements by the number of electron shells/energy levels
14. Chemical formulas and symbols written to represent a reaction
18. The columns on a Periodic Table that arrange the elements by the number of valence electrons in the outermost shell.