Properties of Atoms and The Periodic Table. Ch 16, pg

Transcription

1 Properties of Atoms and The Periodic Table Ch 16, pg

2 Today s Learning Objectives Describe the 5 models of the atom. Be able to arrange the 5 models of the atom in order. Explain why the models of the atom changed over time.

3 Structure of the Atom (16-1a) Atomic theory sounds modern, but it goes back nearly 2500 years Democritus ancient Greek who proposed the atom Atom The smallest particle of an element that retains the element s properties

4 Structure of the Atom Democritus views lost out to Aristotle, who was more famous, so concept forgotten for over 1000 years During middle ages we had the work of the alchemists (early chemists who tried to turn other elements into gold) 1700s Dalton develops first scientific Atomic Theory

5 Structure of the Atom Dalton s Atomic Theory 1. All substances are made of atoms. 2. Atoms cannot be created or destroyed. 3. Atoms of the same element are exactly alike. Atoms of different elements are not alike. 4. Atoms of 1 element join with other atoms of other elements to make new compounds.

6 Structure of the Atom Models of the Atom through time 1. Solid Sphere model (1700) Dalton 2. Plum Pudding model (1904) JJ Thomson Discovered electrons (negatively-charged particles in atom) Imagined them to be floating around in otherwise positive pudding

7 Structure of the Atom 3. Rutherford model (1911) Rutherford discovered the nucleus His model separated the electrons to an area outside the nucleus 4. Bohr model (1913) Bohr put the electrons in planetlike orbits

8 Structure of the Atom 5. Electron Cloud model current model of the atom Electrons don t move in predictable orbits, instead located within regions of the electron cloud

9 Structure of the Atom So why has the model of the atom kept changing over time? In science, hypotheses and models are updated as new discoveries change our ideas. In the case of the atom, the discoveries were the electron (Thompson), nucleus (Rutherford), energy levels (Bohr), and some extraordinarily complex math (basis of electron-cloud model)

10 Today s Learning Objectives Know the 3 subatomic particles Describe the structure of the atom. Be able to compare and contrast the 3 subatomic particles based on properties such as charge, mass, and location. What are quarks?

11 The Structure of the Atom (16-1b) Now that we ve discussed the history what is our current idea of the atom? Very small cm in diameter 20,000,000,000,000,000,000,000 atoms of copper in a penny Atoms The Space Between (RW)

12 The Structure of the Atom In our last chapter we discussed elements With over 115 elements, we need to organize and organize and name them That s a big part of this chapter Handout Periodic Tables

13 The Structure of the Atom Atomic symbols: using one- or two- letter abbreviations for the element names

14 Know the following 20 elements for the elements quiz Symbol H He Li B C N O F Ne Na Chemical Name Hydrogen Helium Lithium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Symbol Mg Al Cl K Ca Fe Cu Ag Au Pb Chemical Name Magnesium Aluminum Chlorine Potassium Calcium Iron Copper Silver Gold Lead Know these things: Name Symbol Note on symbols: Only capitalize first letter Never capitalize second letter

15 The Structure of the Atom Three particles make up the atom 1. Proton 2. Neutron 3. Electron

16 The Structure of the Atom Proton positive particle Symbol = +, p, or p + Charge = +1 Mass = 1 amu amu atomic mass unit Location = nucleus All protons exactly the same

17 The Structure of the Atom Neutron neutral particle Symbol = n Charge = 0 Mass = 1 amu Location = In nucleus All neutrons exactly the same

18 The Structure of the Atom Electron negative particle Symbol = - or e - Charge = -1 Mass = 0 amu (atomic mass unit) Location - outside nucleus All atoms have the same number of electrons as they have protons Evens out the charges All electrons exactly the same

19 The Structure of the Atom Quarks Extremely tiny particles that make up protons and neutrons 1 proton = 2 up quarks and 1 down quark 1 neutron = 2 down quarks and 1 up quark Video on quarks

20 Today s Learning Objectives Know how the atomic number and mass number are different What is an isotope? Given a specific isotope, be able to determine the number of protons and neutrons (and vice versa) Know how to determine the number of electrons. Be able to draw the electrons around a nucleus into the appropriate energy levels.

21 Masses of Atoms (16-2) 20 Elements Practice Particle Review

22 Masses of Atoms Describing Atoms: How are atoms of the elements different? Each element has a different number of protons The number of protons determines the element Atomic number The number of protons in an atom s nucleus

23 Masses of Atoms Yet, all atoms of an element aren t quite the same # of protons is same # of neutrons varies Isotopes Atoms of the same element that have different numbers of neutrons Ex. Hydrogen has 3 isotopes, one with 0 neutrons, with 1 neutron, and with 2 neutrons Draw on board

24 Masses of Atoms How are isotopes alike or different? Isotopes have all of the same chemical and physical properties Different mass in amu Some isotopes are unstable (radioactive)

25 Masses of Atoms Mass number The sum of the number of protons and neutrons in an atom Ex: A typical Helium atom has 2 protons and 2 neutrons, so its mass number is: = 4! Note: The mass number is close to, but not the same as, the Average Atomic Mass on the periodic table. That one is a weighted average of all of the isotopes a tougher calculation

26 Masses of Atoms Naming isotopes Give the name of the element, a dash, then the mass number Ex. Carbon-12 Has a mass number of 12 If carbon has 6 protons, how many neutrons is that? Mass number atomic number = number of neutrons

27 The Periodic Table (16-3a) The number of electrons can be determined by looking at atomic number Atomic number = number of protons In an atom, the # of protons = # electrons too So how many electrons does Helium have? How about Sodium? Argon?

28 The Periodic Table Arrangement of Electrons The actual arrangement of electrons is pretty complex But it can be symbolized with energy levels

29 The Periodic Table Electrons drawn in energy levels First energy level can hold 2 electrons Second energy level can hold 8 electrons Third energy level can hold 18 electrons

30 The Periodic Table Time out for drawing: Draw a Hydrogen atom w/electrons Draw Helium Draw Lithium Draw Neon Draw Sodium Draw Chlorine

31 The Periodic Table (16-3b) Today s Learning Objectives: How is the periodic table organized? Who created the first modern version of the periodic table? How are periods and groups on the periodic table different? What is the significance of being in the same group on the periodic table? Know the 3 regions on the periodic table.

32 The Periodic Table It s the 1860s You know about 63 elements You have to teach them to your students What do you do? Develop a table that will change science forever!

33 The Periodic Table Periodic Table an arrangement of the elements by increasing atomic number and by changes in chemical and physical properties Dmitri Mendeleev created the first useful periodic table Inspired by solitaire! (Video)

34 The Periodic Table Mendeleev noticed properties of the elements formed a pattern Although his pattern had some areas where no known element would fill the spot Left open spots for new elements

35 The Periodic Table Was initially successful Mendeleev used it to predict existence of several new elements, and the properties of them Gallium Predicted properties Actual properties Atomic mass Density 5.9 g/cm g/cm 3 Appearance Soft metal Soft metal Melting point Low 29.7 C

36 The Periodic Table But it wasn t perfect After the proton was discovered, they rearranged it by increasing atomic number (I.e. proton count) the periodicity became more perfect

37 The Periodic Table Parts of the periodic table 1. Periods the rows on the periodic table 2. Groups the columns on the periodic table

38 The Periodic Table Elements in the same groups have similar properties Example: Group 18 - Noble Gases All of the elements in group 18 are gases at room temperature. None of them naturally participate in chemical reactions.

39 The Periodic Table This is the real periodic table

40 It is usually reformatted to be narrower:

41 The Periodic Table 3 Regions on the Periodic Table 1. Metals left of the zig zag 2. Nonmetals right of the zig zag 3. Metalloids on the zig zag

42 The Periodic Table New elements are created in labs All elements numbered 93 and higher are man-made! Made in machines called particle accelerators or atom smashers Newest named elements: #114: Fl = Flerovium #116: Lv = Livermorium