Chemistry

3. A substance composed of one type of atom only
4. An energy level representing the distance of an electron from the nucleus of an atom.
7. Vertical column of elements in the periodic table
11. Separation of a mixture into fractions that differ in boiling points
16. The number of protons in the nucleus of an atom
17. Two or more different atoms held together by chemical bonds
19. The sum of the numbers of protons and neutrons in the nucleus of an atom
20. A subatomic particle that has a positive charge and that is found in the nucleus of an atom

1. Sum of the atomic masses of elements in a compound expressed in grams
2. Negatively charged particle; located outside the atomic nucleus
5. The process of purifying a liquid by boiling it and condensing its vapors
6. A table that shows the elements, their atomic number, symbol, and average atomic mass; elements with similar chemical properties are grouped together
8. The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12; average mass of atoms of an element
9. a technique that separates the components of a mixture on the basis of the tendency of each to travel or be drawn across the surface of another material
10. A process that separates materials based on the size of their particles
12. Smallest particle of an element
13. One of two or more atoms with the same atomic number but with different numbers of neutrons
14. A substance made up of atoms of two or more different elements joined by chemical bonds
15. A horizontal row of elements in the periodic table
18. A subatomic particle that has no charge and that is found in the nucleus of an atom
19. A substance consisting of two or more substances mixed together but not chemically bonded together