Atoms and Matter. Democritus proposed that atoms are tiny, Indivisible particles that make up all matter. The word atom means unable to be divided.

Transcription

1 Atomic Structure 1

2 Atoms and Matter Democritus proposed that atoms are tiny, Indivisible particles that make up all matter The word atom means unable to be divided.

3 Thomson s Atomic model(1898) (Plum-pudding model)

4 How do we know the structure of an atom? Rutherford (1911) bombarded Alpha particles (Helium particles) on a very thin gold foil. Most of the particles passed through, some deflected at large angles 1 in deflected back to its own path.

5 What Rutherford s experiment told us Most of the atom is empty space. There is a very tiny dense core of mass and + charge located in the atom. (Called nucleus)

6 Rutherford s Atomic model (1920) The atom is mostly hollow. The mass and a positive charge are located at the center in a very small portion. Negatively charged particles revolve around the center like the planets revolve around the sun.

7 Photo May, 2013 First Ever picture of Hydrogen Atom! Taken with a quantum microscope 7

8 The 3 sub-atomic particles that make up an atom Protons Neutrons Electrons 8

9 Proton Facts # of protons = the atomic number Positively Charged Unique to each element, its the identity of an element. No two elements can have the same atomic number When the number of protons changes, it is no longer the same element 9

10 Electron Facts Negatively charged Normally, there are equal number of protons and electrons in an atom This means the atom as a whole is neutral in charge (neither positive or negative) 10

11 Electron Facts When you change the number of electrons in an atom, you upset the balance between protons and electrons giving the atom a positive or negative charge IF YOU CHANGE THE NUMBER OF ELECTRONS, YOUR DON T CHANGE THE ELEMENT, YOU JUST GIVE IT A CHARGE 11

12 Neutron Facts Neutron numbers have to be calculated from the periodic table. (Mass # Atomic #) **more on this later They have no charge (neutral) Mass # Atomic # 12

13 Location of Subatomic Particles in the Atom Protons and Neutrons reside in the nucleus 13

14 Location of Subatomic Particles in the Atom Electrons reside outside nucleus in shells 14

15 WHAT IS AN ATOM? UNTIL 4:20 15

16 Take 2, take 3 Take 2 minutes to review your notes and, highlight the important points of the lesson so far. Take 3 minutes to turn to your table partner and share with them what you highlighted 16

17 Using Models 3-D Diagram Flattened Diagram (click below)

18 Mass of sub atomic particles Particle Charge Location Relative Mass (atomic mass unit amu) Proton + (positive) nucleus 1 amu Neutron No charge neutral nucleus 1 amu Electron - (negative) Outside of nucleus in shells.005 amu Where is most of the mass of an atom located? 1 amu = kilograms 18

19 Review Foldable Parts of the Atom 19

20 Atomic Number (# of protons) Atomic Weight/Mass Number Element Symbol 20

21 Multiple ways, mean the same 21

22 What does the Atomic number tell you? Atomic number = # protons in an atom AND.. # of protons = # of electrons # of electrons/# of protons /atomic number 22

23 What does the Atomic Weight tell you? Atomic Weight = # of protons + # of neutrons To calculate # of Neutrons = At.Wt. Atomic number (# of protons) Atomic Wt= # of protons + # of neutrons 23

24 Atomic Weight Why does it make sense that the atomic weight =protons + neutrons? Hint: where is most of the mass of an atom located??? 24

25 What is Atomic Mass? Atomic Mass = Atomic Weight Simply another name for atomic weight, they are used interchangeably! 25

26 Given, (a) (b) (c) (d) You Try It Cu What is the number of protons? Ans: 29 What is the number of electrons in Cu atom? Ans: 29 What is the atomic weight? Ans: 64 What is the number of neutrons? Ans: 64-29=35 26

27 IONS An atom that has a positive or a negative charge due to the LOSS or GAIN of an electron An ION is an atom or compound with a positive or a negative charge 27

28 CATION An atom that has a positive charge due to the LOSS of an electron An atom or compound with a positive charge EXAMPLE Na + - called an CATION due to a loss of an electron 28

29 ANION An atom that has a negative charge due to the GAIN of an electron An atom or compound with a negative charge EXAMPLE Cl - - called a ANION due to a gain of an electron 29

30 IONS You Try it Beryllium gives away 2 electrons. What would its charge be? Nitrogen steals 3 electrons. What would its charge be? 30

31 You Try It Electrons, Protons and Neutrons OH MY! Atomic structure! 31

32 Neutron Facts All elements, naturally occurring, have some atoms that have more or less neutrons than what is reported on the periodic table. For example, look on your periodic table how many neutrons does it say hydrogen has? 32

33 Neutron Facts Atoms of the same element that have a different number of neutrons are called ISOTOPES It is still Hydrogen, just a different form!!!! 33

34 ISOTOPES Atoms with the same number of protons, but DIFFERENT number of neutrons Still the SAME element (because the number of protons doesn t change)! 34

35 ISOTOPES Due to the differing number of NEUTRONS, the atomic weight of each ISOTOPE will be different H H-2 atomic weight H-3 35

36 Average Atomic Weight/Mass Found by averaging all isotopes that occur naturally 36

37 You Try it: Isotopes 37

38 BAG O ISOTOPES 38

39 Electronic Structure The way the electrons in an atom are arranged is called electronic structure Electrons are arranged in shells which are numbered from the nucleus outwards Each shell is capable of holding up to a certain number of electrons 39

40 The HOME of Electrons Electrons live in shells. Only so many electrons can live in each shell Shells Nucleus 40

41 Electronic Structure Electrons are arranged in shells which are numbered: 1, 2, 3, 4, etc, from the nucleus onwards 41

42 Electronic Structure Nucleus Each shell holds a maximum number of electrons 1 st shell 2 electrons 2 nd shell 8 electrons 3 rd shell 8 electrons (proton number 20) 42

43 Maximum # of electrons 1 st shell max. 2 electrons 1 st shell nucleus 2 nd shell max. 8 electrons 3 rd shell max. 8 electrons 4 th shell variable LAST SHELL Max of 8 43

44 Electronic Structure To find the electronic configuration of an atom, we should (1) Fill the electrons into the shell nearest to the nucleus first. This shell can take a maximum of 2 electrons (2) Once this shell is filled, the electrons go to the next available shell which has a maximum capacity of 8 electrons, and so on 44

45 Let s Try Sodium Na How many electrons do we need to put in shells? 45

46 Let s Try Sodium, 23 Na 11 Electronic Structure - 2 Na 1 st shell 46

47 Let s Try Sodium, 23 Na 11 Electronic Structure - 2, 8 Na 1 st shell 2 nd shell 47

48 Let s Try Sodium, 23 Na 11 Electronic Structure - 2, 8, 1 Na 1 st shell 2 nd shell 3 rd shell 48

49 You Try It Draw the electron structure (aka Bohr Model) for Lithium Carbon Calcium 49

50 Valence Electrons Electrons will keep filling shells until all the electrons have a home If an atom has 11 electrons, 2 will fill the 1 st shell, 8 will fill the 2 nd and 1 will fill the 3 rd. This last electron is called the Valence electron Shells 50

51 Electron Dot Diagrams Bohr model vs. Lewis Dot All the electrons vs. Only the Valence shell 51

52 You Try it: Electron Dot Diagrams 52

53 Chapter 1 and 2 53

54 MATTER Classification of Matter Composition of Matter

55 Elements, Molecules, Compounds, Solutions Element composed of identical atoms Molecule - when two or more atoms join together chemically Compound a molecule that contains at least two different elements. A fixed amount Solution variable combination of two or more elements

56 Element matter composed of identical atoms All atoms are the same EX: copper

57 Molecule Composed of identical elements Ex. Oxygen 57

58 Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: salt (NaCl)

59 Solution (Mixture) Variable combination of 2 or more pure substances. Homogeneous Mixture (Solution) even distribution of components very small particles particles never settle EX: saline solution, fresh pickle juice

60 Mixtures Heterogeneous Mixture uneven distribution of components colloids and suspensions EX: granite

61 Mixtures Colloid medium-sized particles Looks cloudy particles never settle EX: milk, fog

62 Mixtures Suspension large particles particles scatter light particles will settle (needs to be shaken) EX: Italian salad dressing (oil, vinegar, and spices)