Warm-up #11 Jan. 25

1. Warm-up #11 Jan. 25 • Atomic Theory • States that matter is composed of discrete units called atoms • The word "atom" comes from the ancient Greek adjective atomos meaning 'indivisible’ Essential Question: When and where do you think mankind originally began to ponder as to what makes up the elements and atoms?

2. Subatomic Particles NameSymbolChargeRelativeActual massmass Electron e- -1 1/1840 9.11 x 10-28 Proton p+ +1 1 1.67 x 10-24 Neutron n0 0 1 1.67 x 10-24 crap

3. Symbols • The symbol of an element contains the mass number and the atomic number: X Mass Number Atomic Number

4. Symbols Rh 104 Find the: • Number of Protons • Number of Neutrons • Number of Electrons • Atomic Number • Mass Number 45 Rhodium - 104

5. History of the Atom • The original idea of the atom came from Ancient Greece (400 B.C.) • Democritus – Greek Philosopher • He and his mentor Leucippus first described that all things were made up of “atoms”

6. Who’s Next? • Late 1700’s – John Dalton – England • Teacher – summarized results of his experiments and those of others in his Atomic Theory. • His idea combined ideas of elements with atoms

7. Dalton’s Atomic Theory • All matter is made up of tiny individual particles called atoms • Atoms of the same element are identical, those of different elements are different • Atoms of different elements combine in whole number ratios to form compounds • Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

8. JJ Thomson • J.J. Thomson – English physicist, 1897 • Made a piece of equipment that explored the properties of cathode rays. • Basically discovered that atoms of divisible

9. Thomson’s Model • Found the electron • Couldn’t find positive (for a while) • Said the atom was like plum pudding • A bunch of positive stuff, with the electrons able to be removed

10. Protons • Proton – positively charged pieces 1840 times heavier than the electron. • Eugene Goldstein used a modified cathode ray • Rutherford predicted its presence in the atom with gold foil experiment

11. Rutherford’s Experiment • Ernest Rutherford was an English Physicist (1910) • Believed in the plum pudding model of the atom. • Wanted to see how big they are • Used radioactivity • Alpha particles – positively charged pieces given off by uranium • Shot them at gold foil which can be made a few atoms thick

12. He Expected • The alpha particles to pass through without changing direction very much. • Because… The positive charges were spread out evenly. Alone they were not enough to stop the alpha particles

13. What He Got

14. How he explained it • Atom is mostly empty • Small dense, positive • Piece at center • Alpha particle are deflected by it if they get close enough

15. Density of the Atom • Since most of the particles went through, it was mostly empty • Because the pieces turned so much, the positive pieces were heavy • Small volume, big mass, big density. • This small dense positive area is the nucleus

16. Bohr’s Model – 1915 • Why don’t the electrons fall into the nucleus? • Move like planets around the sun. • In circular orbits at different levels • Amounts of energy separate one level from another

17. Bohr’s Model • The further an electron is from the nucleus the more energy it has • There is no “in between” energy • It is like a ladder

18. Bohr’s is not right either! • Bohr got closer than we had been so far, but it was still not right. • He gave us the idea of energy levels for electrons. • BUT his idea only worked for one atom

19. Neutrons • No charge • Same mass as the proton • Discovered by James Chadwick during radioactivity experiments in 1932

20. Quantum Mechanical Model • 1925 - Erwin Schrondingerused the results of the experiments done with the hydrogen atom to come up with the quantum mechanical model • This comes from a mathematical solution to the Schrodinger equation • The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations.

21. QMM • Has energy levels for electrons • Orbits are not circular • It can only tell us the probability of finding an electron a certain distance from the nucleus.

22. Modern View • The atom is mostly empty space • Two regions • Nucleus – protons and neutrons • Electron cloud – region where you might find an electron

24. Atomic Theory Timeline Assignment • You are to create a timeline that maps out each significant event throughout history that involves the atomic theory. • There will be at least 8 events (all were covered in the notes) • For each event I want the: • Date • Person • What they contributed (IN COMPLETE SENTENCES). • A drawing or something of what they discovered. They need to be colored.

25. TICKET OUT THE DOOR • What does the atomic number tell you about an element? • What are the three subatomic particles, their relative masses, relative charges, and location(which region of the atom)? • What is a compound? • What is an isotope?

26. Warm-up #12 Jan. 26 An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons • Cations • When an element becomes positively charged it forms a cation • Anion • When an element becomes negatively charged it forms an anion What do you have to lose in order to become positively charged?

27. The Periodic Table • The periodic table is based on the Modern Periodic Law • Came from the QMM • Set up in rows called periods • Indicate the main energy level • Columns called groups or families • Similar properties

28. Dmitri Mendeleev was one of the first scientists to realize there was a trend in the properties of the elements

29. Classifying • We separate the periodic table several ways to help classify the elements • This includes dividing it by families, and type of element

31. Representative – group A • Transitions – group B • We split the table into these 2 major groups • Most of what we deal with deal with is in group A or the representative elements

32. Metal ~ Nonmetal ~ Metalloid • These are three of our other main classifications • Elements that fit into these groups have specific properties

33. Metals • Most metals are solid at room temperature • Which one is the exception? • Mercury – Hg • Generally good conductors of heat and electric current • Sea of free floating electrons • Usually form cations • Usually malleable and ductile

34. NonMetal • Less similarities in the nonmetals • Typically poor conductors of heat and electric current • Solid nonmetals tend to be brittle • Carbon, Sulphur

35. Metalloid • These elements have properties that are similar to both metals and nonmetals • Semiconductors • Can be used to produce superconductors • Boron, silicon, arsenic

36. Periodic Table Assignment • Pick 3 elements, one from each subgroup (metal, nonmetal, metalloid) • Research each element: • Draw the symbol as you would see it on the periodic table • Label the atomic number and mass number • Tell me where the element is found and how we use it • Products, industry, etc. • Describe some of its properties • Draw a picture of what it looks like naturally • These should be colored

37. Warm-up #13 Jan. 27 • Valence Electrons - are the electrons of an atom that can participate in the formation of chemical bonds with other atoms. • Electron dot diagrams - diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule

38. How do Elements form ions and why? • All elements are trying to get the same number of electrons as the nearest noble gas • Far column on the right • This is where valence electrons come in

39. Valence electrons • All atoms have valence electrons • These are the electrons responsible for forming bonds • They are the furthest from the nucleus • They fill the outermost energy level • These determine the properties of the atom, such as stability.

40. Every element can only have 8 valence electrons • They WANT to have 8 like the noble gases • Helium only has 2 electrons TOTAL, so some elements are content

41. Valence Electrons • You can determine how many valence electrons for Group A by looking at the groups number

42. Valence Electrons • We represent valence electrons using electron dot diagrams. • Electron dot diagrams show the element symbol with dots representing the valence electrons

43. Bohr’s Model • Shows ALL of the element’s electrons • 1st – 2e- • 2nd – 8e- • 3rd – 18e- • 4th – 32e-

44. Nitrogen N

45. Aluminum Al

46. Ions • Atoms form ions based on the number of valence electrons • Group VIII A • 8 valence electrons (8 ve-) • What is the charge as an ion? • 0

47. Positive ions are called cations • These are formed when an atom loses electrons • The metals usually form cations • Negativeions are called anions • These are formed when an atom gains electrons • The nonmetals usually form anions

48. When an atoms forms an ion it changes size because it becomes stable • Cations are much smaller the atom in which they form • Anions are much bigger than the atom from which they form

50. TICKET OUT THE DOOR • What does the atomic number tell you about an element? • What are the three subatomic particles, their relative masses, relative charges, and location(which region of the atom)? • What is a compound? • What is an isotope?