1. Chemistry Review Answers

2. 1. Define matter.
Anything that occupies space and has mass.

3. Bonus Question!! What is matter made of?
Either pure elements or combinations of elements called molecules.

4. 2. What are elements?
Elements are the most basic of all substances. They cannot be broken down by normal chemical means. The smallest piece of an element is an atom.

5. 3. How many elements are there?
118 as of December 2015

6. 4. How many elements are man-made?
26 as of December 2015

7. 5. How many elements are naturally occuring?
92, of which 25 are essential to life.

8. 6. What is a compound?
A substance containing two or more elements.

9. 7. Construct a table. Proton 1 +1 Nucleus Neutron Electron 1/2000 -1
Sub-atomic
Particle
Relative Mass
(AMU)
Charge
Where Found
Proton 1 +1
Nucleus
Neutron
Electron
1/2000 -1
Electron Cloud

10. A Helium Atom

11. 8. What is an isotope?
Isotopes of a particular element have the same number of protons and electrons but different numbers of neutrons so their mass is different.

12. Examples Carbon’s atomic # is 6. C-12 has… C-14 has…
Protons – Protons -
Neutrons – Neutrons -
Electrons – Electrons - 6 6 6 8 6 6

13. 9. What is a radioactive isotope?
Isotopes that have unstable nuclei and eject particles and energy at very high speeds. This process is called “decaying”.

14. Uses of Radioactive Isotopes
X-rays – low dose of radiation
CT Scan – Computed Tomography or
CAT Scan – Computed Axial Tomography
- high dose of radiation
- several X-ray images are put together by a computer to create a 3D image

15. Uses of Radioactive Isotopes
Used to image “tubes” (arteries, intestines, bronchial tubes) for medical diagnosis. Thick substance coats tubes then radiographs can see the outlines.

16. Uses of Radioactive Isotopes
Upper GI – Patient drinks thick, milky, chalky liquid full of barium isotope.
Lower GI – Same type of liquid, but the patient does not drink it …

17. Uses of Radioactive Isotopes
As a treatment for cancers.
131 Iodine, 226 Radium,
60 Colbalt

18. Uses of Radioactive Isotopes
Used as a medical tracer. A PET (Positron Emission Tomography) scan uses radioactive glucose to track which part of the brain is working properly.

19. Uses of Radioactive Isotopes

20. Uses of Radioactive Isotopes
Used to discover the age of old items (dating). C-14 is commonly used for dating things that were once alive.

21. Uses of Radioactive Isotopes
C-14 concentrations remain stable in living organisms due to eating. After death, concentrations decrease due to isotope decay.

22. Uses of Radioactive Isotopes
Half-life (T1/2) refers to how long it takes for ½ of the atoms in a radioactive sample to decay.

23. Uses of Radioactive Isotopes
Half-life
Atom (Years)
C ,730
K billion
U billion
Rb billion

24. Sample Half-Life Problem
An archaeological team finds the remains of an ancient campsite. A sample of firewood is dated using C-14. It is known that the same size of firewood found today contains 48 grams of C-14 if alive. The ancient firewood contains 12 grams of C-14. How old is the campfire? C-14 T1/2 = 5,730 years.

25. Sample Half-Life Problem
Alive amount – 48 grams
5,730 years later – 24 grams
5,730 years later – 12 grams
5, ,730 = 11,460
The campfire is 11,460 years old.

26. Sample Half-Life Problem
You are struck down by a speeding Volvo in front of the school and left on the side of the road to rot. An archaeologist 17,190 years from now, while unearthing the remains of Stevenson High School, finds your remains. Carbon dating reveals that your remains contain 5 grams of C-14.

27. Sample Half-Life Problem
How many grams of C-14 did your body have in it when you were alive?
Remains – 5 grams
5,730 years earlier – 10 grams
5,730 years earlier – 20 grams
5,730 years earlier – 40 grams
You had 40 grams of C-14 when you were alive.

28. 10. What is an ion?
An atom or a molecule with an electrical charge resulting from a gain or loss of one or more electrons.

29. Examples of Ions Calcium’s atomic number is 20
Ca+2 has 20 protons and 18 electrons
Chlorine’s atomic number is 17
Cl-1 has 17 protons and 18 electrons
Potassium’s atomic number is 19
K+ has 19 protons and 18 electrons

30. 11. What is an ionic bond?
Atoms with full outer shells are more stable than atoms without full outer shells. When two atoms without full outer shells collide, a transfer of electrons may occur.

31. 11. What is an ionic bond?
When this transfer occurs, the two oppositely charged ions are attracted to each other.

32. 11. What is an ionic bond?

33. 12. What is a covalent bond?
When two or more atoms “share” electrons instead of transferring them.

34. Covalent Bonds

35. 13. What is a hydrogen bond?
Hydrogen has one electron and one proton. Many other atoms are more “electronegative” than hydrogen. This results in hydrogen’s electron spending more time around these other atoms when in a molecule. This leads to molecules that are called “polar molecules”.

36. Polar Molecules
Molecules that have a slightly positive side as well as a slightly negative side.
The slightly positive side (where hydrogen is) tends to attract negative things and this is called hydrogen bonding.

37. Polar Molecules

38. Polar Molecules
Hydrogen
Bond