Chemistry Review

4. (on the P.T.): a column of elements
9. atomic particles found in the nucleus of atom and carry a positive charge (+)
11. is a substance formed when two or more chemical elements are chemically bonded together. Two types of chemical bonds common in compounds are covalent bonds and ionic bonds. The elements in any compound are always present in fixed ratios
13. number: that always contains the same number of protons and electrons
14. accompanied by the release of heat.
17. a substance that takes part in and undergoes change during a reaction
20. a chemical reaction that is accompanied by the absorption of heat, or an organism that generates heat to maintain its temperature. A chemical reaction that works only if heat is absorbed is an example of a reaction that would be described as endothermic
21. Gas: any of the gaseous elements helium, neon, argon, krypton, xenon, and radon, occupying Group 0 (18) of the periodic table. They were long believed to be totally unreactive but compounds of xenon, krypton, and radon are now known
23. Bohr: Danish physicist who proposed a theory for the hydrogen atom based on quantum theory.
24. of Conservation of Mass: the number atoms present BEFORE and AFTER a reaction takes place is ALWAYS the same
25. hard and solid and shiny, electricity, good conductors of heat, ductile, and malleable
26. atomic particles found in the nucleus of atom and has no charge

1. a mark or character used as a conventional representation of an object, function, or process, e.g., the letter or letters standing for a chemical element or a character in musical notation.
2. Mendeleev: Russian chemist who formulated the Periodic Law
3. combination of two or more elements link together
5. (on the P.T.): the side of a table
6. is a substance that is formed when two or more chemicals react. When a chemical reaction takes place, a new substance is often created from the atoms or molecules of the original substances. There are often multiple products formed in a reaction
7. a cause to be deposited in solid form from a solution
8. brittle, not malleable or ductile, poor conductors of heat and electricity
10. it is the most important part of an object, movement, or group, forming the basis for its activity and growth
12. atomic particles that move around the nucleus of an atom and carry a negative charge (-)
15. each of the actual or potential patterns of electron density that may be formed in an atom or molecule by one or more electrons, and that can be represented as a wave function
16. electron: electrons in the outermost energy level of an atom
18. it is a basic unit of a chemical element
19. show both properties
22. is a substance that is made up of one type of atom