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 WHAT IS AN ATOM? UNTIL 4:20 13

14 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 14

15 Location of Subatomic Particles in the Atom Protons and Neutrons reside in the nucleus 15

16 Location of Subatomic Particles in the Atom Electrons reside outside nucleus in shells 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 99.9% of the mass of an atom is in the nucleus 1 amu = kilograms 18

19 Atomic Structure Layered Book 19

20 Symbol of an atom (element) 20

21 21

22 Where in this symbol can you find the chemical symbol, atomic number and mass number? Guesses? Atomic Number (# of protons) Atomic Weight/Mass Number Element Symbol 22

23 Multiple ways, mean the same 23

24 Atomic number Atomic number The number of protons in an atom For an atom, # of protons = # of electrons # of electrons/# of protons /atomic number 24

25 Mass number Mass number = # of protons + # of neutrons To calculate # of Neutrons = Mass number Atomic number (# of protons) Mass number = # of protons + # of neutrons 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 mass number? 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 EXAMPLE Na + - called an CATION due to a loss of an electron Cl - - called a ANION due to a gain of an electron 27

28 IONS You Try it Na gives away 1 electron. What would its charge be? F steals an electron. What would its charge be? 28

29 You Try It Electrons, Protons and Neutrons OH MY! Atomic structure! 29

30 Neutron Facts All elements, naturally occurring, have some atoms that have more or less neutrons than what is reported on the periodic table. Atoms within the same element that have a different number of neutrons are called ISOTOPES 30

31 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)! 31

32 ISOTOPES Due to the differing number of NEUTRONS, the mass of each ISOTOPE will be different He-1 He-2 He-3 32

33 You Try it: Isotopes 33

34 BAG O ISOTOPES 34

35 Electronic Structure The way the electrons are arranged is called its 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 35

36 The HOME of Electrons Electrons live in shells. Only so many electrons can live in each shell Shells 36

37 Electronic Structure Electrons are arranged in shells which are numbered: 1, 2, 3, 4 from the nucleus onwards Shell no. Maximum no. of electrons Name 1 2 Duplet 2 8 Octet 3 8 (for atoms with proton number 20) Octet 37

38 Electronic Structure Nucleus 1 st shell 2 electrons 2 nd shell 8 electrons 3 rd shell 8 electrons (proton number 20) 38

39 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 39

40 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 40

41 Electronic Structure Sodium, Na Electronic Configuration 2, 8, 1 Na 1 st shell 2 nd shell 3 rd shell 41

42 You Try It Draw the electron structure (electron dot, lewis dot) for Lithium Carbon Calcium 42

43 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 43

44 Electron Dot Diagrams Bohr model vs. Lewis Dot 44

45 You Try it: Electron Dot Diagrams 45

46 MATTER Classification of Matter Composition of Matter

47 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

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

49 Molecule Composed of identical elements Ex. Oxygen 49

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

51 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

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

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

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