The Periodic Table. S Objective: Investigate the development of the periodic table as a method of organizing elements.

Transcription

1 The Periodic Table S Objective: Investigate the development of the periodic table as a method of organizing elements.

2 The early development Newlands used atomic mass in octaves saying that every 8 th element shares similar properties (1863) Dobereiner used physical properties in triads saying certain groups of 3 elements share similar properties (1817)

3 Julius Mayer Meyer organized a table with 28 elements based on the reactivity of the atoms. Also found a pattern when comparing the volume of an atom to its mass This was the first organized periodic table that was beginning to make sense. Meyer could predict some elements that were not discovered yet due to the periodic (repeating) nature of his findings

4 Dmitri Mendeleev Worked independently from Mayer but came up with similar conclusions Systematically placed elements into a organized table based on atomic masses Found that based on the 63 elements known at the time in 1869, the properties of elements are based on mass. He organized these elements into families, or groups, which all had the same amount of valence electrons

5 Mendeleev s first table Ordered his table based on mass and left blanks where he thought elements (that had not yet been discovered) should be

6 Henry Mosely In 1901 Mosely essentially just expanded on Mendeleevs work but ordered the periodic table once more according to proton number (atomic number) This ironed out some difficulties with Mendeleevs table Created the period table with each succeeding element having one more proton and electron than the former element Elements that are arranged according to atomic number and exhibit a reoccurring pattern is called periodic law

7 Your Task With your periodic tables have a table discussion on what you observe the periodic table being ordered in Be prepared to answer and explain this question: Do you think their are any groups in the periodic table that have atoms sharing similar properties? Each table is responsible for filling out a Bohr Diagram sheet and labeling the board with your atoms!

8 18 Lets pause and think about what this means. Take a look at your periodic table for a hint! Look at the columns and look at the rows

9 The periodic table Two important parts of the periodic table that we have today come from the vertical columns and the horizontal rows Horizontal rows are called Periods Vertical columns are called Groups or Families.

10 Groups/Families The International Union of Pure and Applied Chemistry (IUPAC) labels the groups 1-18 from left to right. Somethings labeled with Roman Numerals I VIII with A and B groupings Elements in the same family = same properties and same valence electron number The number of valence electrons equals the Roman Numeral number or the last digit in the IUPAC labeling

11 Families of the period table In grade 9 we will be looking at 6 different families in the period table Alkali Metals, IA or group 1 Alkaline Earth Metals, IIA or group 2 Chalcogens, VIA or group 16 Halogens, VIIA or group 17 Noble Gasses, VIIIA or group 18 Hydrogen (a family by itself) More families or groups do exist but we will look at these a little more closely

12 Before we continue. Please have some different coloured pencil crayons at your table to share! Red Light Blue Light Purple Yellow Orange Dark Blue Dark Purple

13 Alkali and Alkaline Earth Metals Some of the most reactive substances known, as you travel down the column the elements increase in reactivity Never found uncombined in nature, they are always chemically bonded with something else since they are so reactive Are a part of group 1 or (IA) and group 2 (IIA) Alkali Metals have one valence electron Alkaline Earth Metals have two valence electrons

14 So How reactive? Zo8dTcU&feature=player_embedded

15 Chalcogens and Halogens Also very reactive elements exist in these families but act differently than the Alkali and Alkaline Earth Metals Usually not found by themselves in nature Are a part of group 16 (VIA) an 17 (VIIA) Chalcogens have 6 valence electrons, Halogens have 7 valence electrons

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17 So How reactive? Chlorine is a part of the Halogen family and in its gas form can be deadly to human But we also clean our pools with small amounts of chlorine as well Oxygen is a part of the Chalcogens, and we need it to breathe, but pure Oxygen gas is extremely combustible and very dangerous around open flame

18 Noble Gasses Unlike all the other families that we have been discussing, the Noble Gasses are extremely unreactive! They are a part of group 18 (VIIA) Full valence shell! The Noble Gasses can be found in Earth s atmosphere in small amounts

19 Hydrogen Due to Hydrogens special properties it has its own family A part of group 1 (sorta) Has 1 valence electron Bonds with a variety of other elements Makes up the majority of matter in the universe Nuclear fusion starts with Hydrogen

20 So why is Hydrogen so Special?

21 What about the rest of the periodic table? The Transition Metals are the largest group in the table and span from group 3 12 (B group on the table) The number of valence electron depends on their oxidation number and ion charge (next year) Gold, Iron, etc

22 What about those last two rows underneath? These are actually a stem off from the Transition Metals The lanthanide and actinide metals (leave them uncoloured) Sometimes called the Rare Earth Metals All radioactive and many are used in nuclear reactors for fission (a technique to produce energy)

23 Definitions can be filled out!

24 Do Both! Your Task Objective: Investigate the development of the periodic table as a method of organizing elements. 1. How is the periodic table (as we see it today) ordered and arranged? 2. Pick one of the families we have discussed in this lesson, list at least 3 elements that belong to that group, and list something special about an element in that group 1 mark for response 1 mark for proper sentence structure 3 mark for response 1 mark for proper sentence structure 6 marks total