1. Chapter 4
The Atom – Part 2

2. Lord Ernest Rutherford (1871 – 1937)
Discovered the nucleus of the atom.
Pioneered the orbital theory of the atom.

3. Rutherford’s Gold Foil Experiment

4. Rutherford’s Gold Foil Experiment

5. Rutherford’s Nuclear Model of the Atom
The nucleus is very small, dense, and positively charged.
Electrons surround the nucleus.
Most of the atom is empty space

6. Subatomic Particles PARTICLE SYMBOL CHARGE MASS (amu) LOCATION
electron e- -1 0
orbit nucleus
proton p+ +1 1
inside nucleus
neutron n0

7. Alchemy “The Golden Rule”

8. The number of protons in the nucleus of the atom (atomic number = Z) determines the atoms identity
Gold Atom Lead Atom

9. Mass Number
The sum of the protons and neutrons in the nucleus of an atom.

10. What element is represented below?

11. Carbon - 12 This is the symbol for the isotope carbon-12.
Atomic number is 6.
Mass number is 12.

12. Isotopes
Isotopes are different types of atoms of a chemical element, having the same number of protons in the nucleus, but having different numbers of neutrons in the nucleus.
Isotopes therefore have the same atomic number but different mass numbers.
There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms.
Isotopes of a single element possess almost identical properties.

13. Isotopes

14. Carbon - 12
Write the symbols for carbon-13 and carbon-14.

16. What is the average mass of a carbon atom?
12.01

17. Atomic Mass The atomic mass of carbon is 12.01 amu.
Atomic mass is the average mass of all the isotopes of an atom. It takes into account the different isotopes of an element and their relative abundance.

18. Common Uses of Isotopes
Isotope Analysis
Radiometric Dating
Nuclear Medicine:
Magnetic Resonance Imaging (MRI)
Positron Emission Tomography (PET scans)

19. Importance of Isotopes

20. Radiometric Dating

21. Carbon Dating

22. Nuclear Medicine refers to imaging techniques that use radioactive isotopes to detect and treat disease. Magnetic resonance imaging (MRI) and positron emission tomography (PET scans) are examples.

23. MRI PET scan

24. MRI vs. PET
Magnetic Resonance Imaging (MRI) is produced by measuring the magnetism of spinning electrons and protons and their interactions with nearby atoms when they absorb energy. This provides information about the chemical structure of organic molecules. MRI uses a magnetic field from super-cooled magnets and can often distinguish more accurately between healthy and diseased tissue. A contrast agent is usually used. MRI can provide pictures from various angles and construct a three dimensional image. Positron Emission Tomography (PET) scans measure emissions from positron-emitting molecules. Because many useful, common elements have positron emitting forms (carbon, nitrogen, and oxygen), valuable functional information can be obtained. The PET shows molecular function and activity not structure, and therefore can often differentiate between normal and abnormal (cancerous / tumor) or live versus dead tissue. PET scans are usually used to compliment rather than replace the information obtained MRI scans.

25. An atom of vanadium contains 23 electrons
An atom of vanadium contains 23 electrons. How many protons does it contain?
23 p+

26. An atom of silver contains 47 protons. What is its atomic number?

27. An “atom” of sodium contains 11 electrons. What is its atomic number?

28. An atom contains 37 protons. What element is it?
rubidium

29. How many electrons, protons and neutrons are in an atom of actinium with a mass number of 221?

30. How many electrons, protons and neutrons are in an atom of rhodium-105?

31. Homework
Chapter 4 Worksheet 1 (due Monday)