1. Unit 2-The Structure of the Atom & the PT Textbook Ch.4-5 (p.110-173) How can the periodic table be used as a tool to help describe the structure of an atom?

2. Structure of Atoms O Atoms are the basic unit of matter and all have a similar structure

3. The nucleus Neutrons O Neutral particles (no charge) inside the nucleus of the atom O Mass = 1 amu (atomic mass unit)

4. The nucleus Protons O Positive particles (charge = +1) inside the nucleus of the atom O Mass = 1 amu

5. Outside of the nucleus Electrons O Tiny negative particles (charge = -1) that orbit the nucleus of the atom O Always moving O Mass = 0 amu O Located in the electron cloud in energy levels (pathways around the nucleus where electrons move)

6. Diagram of Atom Neutrons Protons Nucleus Electrons Energy levels Electron cloud

7. The PT & Element Symbols Element – the most simple type of pure substance O Contains one type of atom Periodic Table – a table of all of the elements arranged in rows by atomic number and in columns by properties of the elements

8. The PT & Element Symbols

9. O The periodic table “faceplate” Element name Atomic number Element symbol Atomic mass

10. The PT & Element Symbols O Atomic Number – the number of protons in an atom O It identifies the element O The periodic table is arranged by increasing atomic number

11. Building Atoms 1. NEUTRAL ATOMS (charge = 0) HAVE THE SAME NUMBER OF PROTONS AND ELECTRONS. e.g., Nitrogen has ___ p + and ___ e - Charge = #p + - #e -

12. Building Atoms 2. ATOMS OF THE SAME ELEMENT CAN HAVE DIFFERENT NUMBERS OF NEUTRONS. O These atoms are called isotopes. O Isotope – atoms of an element that have a specified number of neutrons e.g., one isotope of carbon has 6 neutrons, while another has 7

13. Mass of Individual Atoms O The mass of an atom depends on the number of protons and neutrons. O Atomic Mass Unit (amu) – the unit used to mass atoms Mass Number = #p + + #n 0

14. Mass of Individual Atoms Hyphen notation element name (or symbol) – mass number e.g., carbon atom (6p +, 6n 0 ) carbon-12 or C-12 carbon atom (6p +, 7n 0 ) carbon-13 or C-13

15. Mass of Individual Atoms Nuclear symbol notation X = element symbol A = mass number Z = atomic number e.g., carbon atom (6p +, 6n 0 ) carbon atom (6p +, 7n 0 )

16. Determining the Number of p +, n 0, e - O For neutral atoms… # p + = atomic number # n 0 = mass number - # p + # e - = # p + - charge …if neutral, # e - = # p +

17. Determining the Number of p +, n 0, e - What about if the atom is not neutral??? O We form an ion. O Ion : atom or group of atoms with an overall positive or negative charge

18. Determining the Number of p +, n 0, e - A N(egative) ION Anion (negative ion) = # e - increases … gains e -

19. Determining the Number of p +, n 0, e - Cation (positive ion) = # e - decreases … loses e - I’ve lost my CAT ION. Are you sure? Yes, I’m positive.

20. Building Atoms “Cheat Sheet” Practice until you know this!!! # p + # n o # e - Atomic #Mass #ChargeHyphen notation Nuclear Symbol Atomic number Mass # - #p + #p + - charge # p + #p + + #n 0 #p + - #e - Element – mass number A = mass # Z = atomic # X = element

21. Give It Some Thought… Hyphen Notation Atomic # Mass # p+p+ n0n0 e-e- Nuclear Symbol O - 18 8 - 75 33 33 20 22 18

22. How are masses of elements on the periodic table determined? O You will have 10 minutes to examine the table of student test scores for five tests they have taken and complete the following Q’s. TESTStudent AStudent B 19576 27488 38290 49281 5 72 AVERAGE GRADE

23. How are masses of elements on the periodic table determined? 1. Calculate the average grade for students A and B and enter the average in the table above. 2. If you only know a student’s average, can you tell what the student’s individual test scores were? Explain. 3. Suppose student C had an average of 83%. On EACH of his five tests he scored either a 65% or a 95%. Which score occurred more often? Explain. 4. What if the teacher decided that test one would could for 40% of the final grade, test two would count for 30% of the final grade, and each of the other tests would could for 10% of the final grade. Calculate the new average for each student. (NOTE: This is called the weighted average.)

24. Average Atomic Mass (AAM) O Most elements occur naturally as mixtures of isotopes O Each isotope has its own atomic mass, which we estimate as the mass number of the isotope O The percentage of each isotope in the naturally occurring element on Earth is nearly always the same, no matter where the element is found. This percentage is known as the isotope’s percent abundance

25. Average Atomic Mass (AAM) O AVERAGE ATOMIC MASS: the weighted average of all of an element’s isotopes Calculating Average Atomic Mass (AAM)

26. SAMPLE PROBLEM Naturally occurring copper consists of 69.17% copper- 63, which has an atomic mass of 62.93 amu, and 30.83% copper-65, which has an atomic mass of 64.93 amu. What is the atomic mass of copper? ISO #1: (62.93amu)(69.17/100) = 43.53 amu ISO #2: (64.93amu)(30.83/100) = 20.02 amu AAM = 43.53 amu + 20.02 amu = 63.55 amu NOTE: THIS CALCULATED AVERAGE ATOMIC MASS IS THE MASS LOCATED ON THE PT!