1. 1 Atomic Structure and the Elements

2. 2 What is an atom? An atom is the smallest particle of an element. Atoms make up all matter. + + 1 AMU

3. 3 Basic Structure of the Atom Nucleus - center of the atom that contains: – Protons - (p+) - positively charged – Neutrons - (n) - no charge Energy Levels / Orbits - paths that electrons (e-) travel around the nucleus - In a neutral atom: Number of protons (+)= Number of electrons (-) – Electrons – (e-) – negative charge Nucleus with Protons & Neutrons Energy Levels with Electrons + + o o

4. 4 Basic Structure of an Atom Each proton and neutron has 1 AMU Electrons do not have much mass compared to protons and neutrons so we don’t count any mass for them + + 1 AMU AMU is an atomic mass unit. o o

5. 5 Where did the Atomic Theory come from? John Dalton (1766-1844) –Published detailed theory in 1808 –Elements are composed of atoms –Atoms of different elements have different properties –Atoms are NOT changed by chemical reactions, just rearranged –Compounds are defined by the number, type and proportion of atoms

6. 6 Expanding the Theory Thomson (1856-1940) –Identified the electron (1897) –Found it had a negative charge –Positive sphere and negative electrons embedded –Atom is neutral-positive cancels negative

7. 7 Developing the Theory Rutherford - discovered that atom has a nucleus (1911) Bohr-discovered electrons orbit nucleus (1915) Schrodinger-discovered electron cloud (1926) Chadwick-discovered neutrons (1932)

8. 8

9. 9 You should notice the numbers are getting bigger from left to right and from top to bottom.

10. 10 Let’s take a closer look at all those numbers…

11. 11 Element Name Atomic Number Element Symbol Atomic Mass (# of protons and # of electrons) (total # of protons and neutrons) (1 st letter capital & if a second it is lower case letters) Be 9.01 Beryllium 4

12. 12 Chemical Symbols Be 9.01 Beryllium 4 Abbreviated way to write the name of an element One capital letter or one capital letter and one lower case letter Some symbol abbreviations are for the LATIN name for the element

13. 13 9 - 4 = 5 If the atomic number tells me the # of Protons and # of Electrons… How do I figure out the number of Neutrons? Be 9.01 Beryllium 4 Use the formula below: Atomic Mass - Atomic Number = # of Neutrons P = 4 E = 4 N = ?

14. 14 5 Neutrons 9 - 4 = 5 Be 9.01 Beryllium 4 Okay – If this tells me the # of Protons and the # of Electrons… How do I figure out the number of Neutrons? Easy – use the formula below: P = 4 E = 4 N = Atomic Mass - Atomic Number = # of Neutrons

15. 15 N 14.01 Nitrogen 7 What are the numbers of protons, electrons and neutrons? F 18.98 Fluorine 9 Cl 35.45 Chlorine 17 Let’s Practice.

16. 16 What is an Isotope? A given Element usually has differing amounts of neutrons. These different forms are called isotopes.

17. 17 Let’s take hydrogen as an example: 1 Hydrogen H 1.01 As you can see from the atomic mass ( 1.01 ) the most naturally abundant form of hydrogen does not have a neutron. However, in rare instances isotopes form. Below are the isotopes of hydrogen: …. are isotopes of hydrogen.  Protium  Deuterium  Tritium Isotopes - Continued

18. 18 Isotope Notation C 12 6 Mass Number Atomic Number How many protons, electrons and neutrons? Protons =6 Electrons = 6 Neutrons =12 – 6 = 6 Carbon - 12 Mass Number Mass number superscript – superman flying Atomic Number subscript - submarine

19. 19 C 14 6 Mass Number Atomic Number Carbon - 14 How many protons, electrons and neutrons? Protons =6 Electrons = 6 Neutrons =14 – 6 = 8 Isotope Notation - Continued

20. 20 N 16 7 Example 1: Example 2: Magnesium - 24 Example 3: 10 Neutrons How many e-?, P?, n? What element? Write this element as demonstrated in Examples 1 & 2. How many protons, electrons and neutrons? Which example(s) are isotopes?

21. 21 What are Bohr Models? Neils Bohr devised a method for drawing models to represent the atoms nucleus and their electron arrangement because the atoms are too small to see. These models are easy to draw – if you follow the steps!

22. 22 Drawing Bohr Models Step 1: Write down the # of protons, electrons and neutrons for each atom’s element. F 18.98 Fluorine 9 (Atomic Number) #Protons = 9 (Atomic Number) #Electrons = 9 # Neutrons = atomic mass – atomic # # Neutrons = 19-9=10 Fluorine = F

23. 23 Drawing Bohr Models - Continued Step 2: Draw a nucleus inserting the # of protons and # of neutrons that are inside. n = p = 10 9 # electrons = 9 # protons = 9 # neutrons = 10 Fluorine = F

24. 24 Drawing Bohr Models - Continued Step 3: Draw the # of energy rings around the nucleus by what row it is in on the Periodic Table. Fluorine is in row #2 so, I need to draw 2 rings around the nucleus. n = p = 10 9 # of rings = row number

25. 25 Drawing Bohr Models - Continued Step 4: Place the electrons on the correct energy ring – filling each to capacity. N = P = 10 9 Energy Levels are Identified as: 1 st Level –holds 2e- 2 nd Level –holds 8e- 3 rd Level –holds 8e- 1 2 Remember we need to have 9 electrons total for fluorine! 3 4 5 6 7 8 9

26. 26 2 Max # of Electrons Energy Level 82 1 8 3 N = P = 10 9 1 2 3 4 5 6 7 # Electrons = 9 # Protons = 9 # Neutrons = 10 Complete Bohr Model Fluorine = F 8 9

27. 27 Happy / Stable Elements Elements that have a full outer ring of electrons are called “happy” atoms. 2 Max # of Electrons Energy Level 8 2 1 8 3 Meaning that – that ring can’t hold any more electrons. So, if the 2 nd ring has 7 electrons in its outer ring – it is still hungry for the 8 th electron – needing it to be “happy.”

28. 28 The last ring or outer shell of the atom is called the... Remember the # of rings that you drew in the Bohr model is equal to the Row number that the element is in on the Periodic Table. 16 S 32.07 17 Cl 35.45 18 Ar 39.95 10 Ne 20.18 9 F 19.00 13 Al 26.98 14 Si 28.09 15 P 30.97 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 2 He 4.0 Fluorine energy level= 2 Fluorine = Row 2 Happy / Stable Elements Valence shell or outer energy level

29. 29 The number of electrons in that last ring or outer energy level are called the... Valence Electrons Happy / Stable Elements 16 S 32.07 17 Cl 35.45 18 Ar 39.95 10 Ne 20.18 9 F 19.00 13 Al 26.98 14 Si 28.09 15 P 30.97 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 2 He 4.0 Fluorine Valence # = 7 Fluorine = Column VIIA Valence electrons are important because you will use them to make compounds.