Intro to Chemistry

1. Intro to Chemistry

2. Atomic Structure • Nucleus- center of an atom -contains protons (which are positive) -contains neutrons (which are neutral) Ex- Sodium:

3. Atomic Structure Outside the Nucleus: • Electrons (which are negative) surround the nucleus in energy levels • Outermost electrons are called valence electrons

4. An atom is defined by the number of PROTONS IT HAS!!!

5. Atomic Mass Unit (AMU) • The unit of measurement for an atom is an AMU. It stands for atomic mass unit. • One AMU is equal to the mass of one proton.

6. Atomic Mass Unit (AMU) • There are 6 X 1023 or 600,000,000,000,000,000,000,000 amus in one gram. • (Remember that electrons are 2000 times smaller than one amu).

7. Subatomic Particles Organized

8. Subatomic Particle Organized Atomic Mass

9. Try it out!Read pp 104-108 then do #3, 4, 5 on page 110

10. The Periodic Table can tell us a lot about the elements.

12. What’s in a square? • Chemical Symbol- letter representing the atom (sometimes from Latin) • ALWAYS write the first letter capital and second letter lower case • Ex- Cu, Fe, Rb

13. Symbols • All elements have their own unique symbol. • It can consist of a single capital letter, or a capital letter and one or two lower case letters. C Carbon Cu Copper

14. Atomic number = number of protons • Don’t kill anyone in my class today! • Mass number = # protons + # neutrons • Don’t use the one on the PT unless you have to! That is an average! Use the Mass # given for that element!

15. Calculating Neutrons is a simple algebraic problem… • Atomic Mass = protons + neutrons • Atomic Number = protons • Write the equation… • Mass # = protons + neutrons • #Neutrons = (mass number – atomic number)

16. What about Electrons? In a NEUTRAL atom, every + (proton) is balanced by a –(electron). Therefore, in a neutral atom, protons=electrons and you can use the following mneumonic: A = P =E (atomic #) = (protons) = (electrons)

17. Complete the table below using the information given for each atom.Atom A has 3 protons and 4 neutrons.Atom B has 11 protons and 12 neutrons.Atom C has an atomic number of 19 and a mass number of 39.Atom D has an atomic number of 17 and a mass number of 35.

18. Complete the table below using the information given for each atom.Atom A has 3 protons and 4 neutrons.Atom B has 11 protons and 12 neutrons.Atom C has an atomic number of 19 and a mass number of 39.Atom D has an atomic number of 17 and a mass number of 35.

19. Try it out! (Blue Worksheet)

20. How do we Draw Atoms? • Lewis Dot Diagrams Bohr Models

21. How to draw a Bohr Model • Draw a nucleus & put protons and neutrons inside. • (may use a square shape so you don’t draw any electrons on it) • Remember the p=e in a neutral atom, so begin putting electrons on the energy levels until you use them all up. • Fill energy levels in order (can’t put any in 2nd shell until you’ve filled the first)

22. Drawing Bohr models, cont… Helpful hints: Draw electrons at each of the four “corners”, then double up Write the number of electrons you drew (in parentheses) on each energy level to help you keep track.

23. Electron configurations (Bohr Models)

24. But…that can be a pain… • Most of the time we only really care about the valence electrons • Valence Electrons- electrons in the outermost shell • Also the GROUP NUMBER!!!

25. Valence Electrons- • Find the number of valence electrons by counting over the rows (skipping transition metals) • See next slide

27. Valence Electrons are what react!

28. How to draw a Lewis Dot Structure • Find the group # (top of the row on the PT) • Write the symbol. • Draw dots around the symbol equal to the group number (if group 2- draw two dots) • Place dots one at a time around the top, right, bottom and left side of the atom before you double any up.

29. How to draw a Lewis Dot Structure • Find the group # (top of the row on the PT) Let’s do Phosphorus • Write the symbol. P • Draw dots around the symbol equal to the group number (if group 2- draw two dots) • Place dots one at a time around the top, right, bottom and left side of the atom before you double any up.

30. Octet Rule- Most atoms want to have 8 electrons in their outer shell.

31. Octet rule exceptions… • (octet rule=Most atoms want to have 8 electrons in their outer shell) • Helium- • What is its group number? • Why doesn’t it make sense to draw that many dots? • Because it is easier for it to fill that first shell which only needs two electrons • Other- Exceptions: • _____ , _____ , _____ , _____

32. Elements with a full outer shell naturally

33. Lewis Dot Structures

34. Atomic Mass Mystery… • Look at the atomic mass for Oxygen. What does it say (exactly?) • 15.9999 • What is the atomic mass? • P + N • So what the heck!?!?! • Average of the actual isotopes on Earth!!!

35. How can we change the mass of an element? • We can’t mess with protons, but what CAN we “mess with?” • Neutrons… • What would that change about the atom? • Changes the MASS • Get an ISOTOPE

36. Isotopes • Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons. • Examples • Cl-35 vs. Cl-37 17P 17P 18N 20N

37. How to write isotopes… • Mass/Hyphen Notation: • Especially important for a form of the isotope that is NOT the “usual” • Write the symbol, a dash, and the mass # for that isotope • Ex’s • C-14 • C-12

38. How to write isotopes… C Mass # Atomic # (=p) • Nuclear Symbol Notation • Includes the symbol, atomic #, and the mass # for that isotope • Ex’s 14 6

39. What else CAN we “mess with?” • Already know…Neutrons… • Get an ISOTOPE, changes the mass • But what if I mess with Electrons… • What would that change about the atom? • Changes the CHARGE • Get an ION

40. Intro to Ions

41. How are these ions made? Can you mess with protons? Would messing with neutrons do anything to the charge? What must you mess with??? What charge does an electron have? So what would happen to the atom if they LOSE one? Would they get more positive or more negative overall???

42. IONS • If you mess with the electrons you change the overall charge of the atom…an atom that is no longer neutral is called an ION. • ANION- has a negative charge • Means you added an electron! • CATION- has a positive charge • Means you lost an electron

43. Families on the Periodic Table

44. Elements • Science has come a long way since Aristotle’s theory of Air, Water, Fire, and Earth. • Scientists have identified 90 naturally occurring elements, and created about 28 others.

45. Elements • The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe.

46. Mendeleev • In 1869,Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table. • He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties.  • Blank spaces were left open to add the new elements he predicted would occur. 

47. Periodic Table • Organizes elements in a particular way • All the elements in this column (“family”) have similar properties. That’s why they are grouped together.

48. EX- Valence electrons can be determined from the group number!

49. What does it mean to be reactive? We will be describing elements according to their reactivity. • “Reactive Elements” do not have a full outer shell of electrons. Therefore, they will “react” with other elements to get a full outer shell.

50. Let’s Color