CH 4 The Periodic Table

Transcription

1 CH 4 The Periodic Table

2 Finding patters and order among the known elements 1700 s metals and non-metals 1800 s new lab techniques= new discoveries (Line Spectroscopy) JW Dobereiner Triads John Newlands Octaves elements song

3 Mendeleev makes the first coherent table Mendeleev b.1834 He arranged the elements by increasing atomic mass Created a table with gaps for as yet unknown elements Predicted exact properties of these elements Recognized valency as a common property within a group

4 valence electrons The electrons that determine the character of the element (or group of elements) The highest energy (outermost) s and p electrons Example Phosphorous = 1s 2 2s 2 2p 6 3s 2 3p 3 2 outer s + 3 outer p = 5 valence electrons (look at the ones digit in the group #)

5 Warm up How many valence electrons do the following elements have? Mg P Cl Ar Kr

6 Current Periodic Table Organization Each square represents an element. Each element is a part of 1 period and 1 group. Periods are the rows Groups are the columns. Groups are also called families.

7 Periodic Law: Henry Moseley 1. Repeating physical and chemical properties as you increase in atomic number. 2. Amount of Positive Charge (atomic number) in an element was a fundamental property 3. Adjusted Mendeleev s table by arranging elements by Atomic Number (# of protons). rather than Average Atomic Mass

8 IUPAC system of naming families Groups numbereed 1-18 Group 1 = far left Group 18 = far right Replaced competing systems used in the US and Europe.

9 Common family names: 1 = Alkali Metals 2 = Alkali Earth Metals 17 = Halogens 18 = Noble Gases others: 14= 15= 16=

10 Noble Gases: The most stable family 1. Outer s and p sublevels filled. 2. Not reactive 3. Group 18, formerly referred to as Inert Gases

11 Electron Configuration Shortcut Write e- config for: 1. Neon 2. Sodium Locate the element on the periodic table then: 1. backtrack to the previous noble gas 2. [bracket] the symbol. 3. add the remaining electrons based on their block and period 3. Magnesium

12 Write the following e- configurations using the noble gas shortcut 1. Selenium (Se) 2. Iron (Fe) 3. Radium (Ra)

13 Warm Up What are the family names for group 1 and group 2 elements? Group 1 Alkali Metals Group 2 Alkali Earth Metals List 3 halogens. Write their shortcut electron configuration Halogens = Group 17 Smallest = F Cl, Br

14 Main Group elements s-block (groups 1,2) & p-block (groups 13-18) Valence electrons can be predicted based on family location for these elements.

15 Transition metals The d-block (groups 3-12) Valence electrons less predictable Many of the elements we think of as metals are in this block. i.e. gold, silver, zinc, iron, copper.

16 Inner Transition Metals The f-block Also known as: Lanthanides-Actinides Most are rare and radioactive Of great use in electronics, batteries, energy, and weapons.

17 Electron configurations Noble Gas shortcut Titanium (Ti) Rubidium (Rb) Xenon (Xe)

18 Warm Up: What are three names for the elements and ?

19 Periodic Properties Lab Quantify relationships within families: Density Solubility Density: displacement, use graphing to determine an element not measured Solubility: # of reactions with ion pairs

20 Element categories: Metals CONDUCT ELECTRICITY Non Metals DO not conduct electricity Metalloids/semi-metals Are semi-conductors of electricity

21 Periodic Trends Properties of elements can be predicted by their location on the periodic table Changes in these properties can be predicted as you move across or down from a particular element. Warm UP: What subatomic particle transfers atoms in a chemical reaction?

22 Atomic Radius ½ the distance between 2 like atoms in a molecule. Trend: The size increases as you move down The size decreases as you move across

23 Atomic radius trend explained: As you move down: The valence electrons are in higher energy levels. This makes the atom larger As you move across: The electrons are pulled by increasingly dense positive charge (Effective Nuclear Charge Increases) This pulls the electrons closer = smaller

24 Ionization Energy The energy needed to remove 1e - from an atom in the gas phase. The energy is measured in KJ/mol Kilojoules per mole (we ll learn about mole later) The easier it is to remove an electron, the more reactive the element may be.

25 Ionization energy trend *Alkali metals in water Li 520 kj/mol Na 495 kj/mol K 415 kj/mol As you move down IE decreases. As you move across IE increases. Be 900 kj/mol

26 Trends from the lab Density From group 14 carbon family C 2.25 g/ml Si 2.33 g/ml Ge 5.32 g/ml Sn 7.31g/ml Pb g/ml Increases going down a group Solubility From group 2--- alkali metals Mg -no solids Ca - 1 solid Sr- 2 solids Ba- 3 solids Solid formed is called a precipitate.

27 Determine the trend of these values:

28 Electronegativity Attraction of electrons. (How bad do you want to hold onto an electron?) Calculated value using the Pauling scale. 4.0 is the highest value Fluorine is the most electronegative element. Helps predict type of bonding between atoms. Share electrons (covalent) Steal electrons (ionic)

29 Electronegativity Fluorine has the configuration: [He] 2s 2 2p 5 F is 1 electron from having the noble gas electron configuration of Neon. Fluorine has a very strong attraction to electrons. Electronegativity value for Fluorine is 4.0 As you move away from Fluorine: DOWN E n decreases. LEFT E n decreases.

30 Other periodic trends Electron affinity- Similar to electronegativity Measure of electron wanting when it is unbonded all by itself Electronegativity is a measure of how tightly an electron is held Increases across, decreases down the same as electronegativity

31 Warm Up Put the following in order of smallest atomic radius to largest: Si, Sr, P, Ar, Na, Li Put the following in order of greatest electronegativity to least: P, F, Cs

32 Creatively represent Mendeleev s Garden Art Criteria Color, a picture or pictures, variable texture, no use of marker Academic Criteria represent the idea of valence (valency) and or periodicity. include a quote or excerpt from the book Other topics you may include: Periodicity CRC handbook The missing elements, missing family Trends in the table Oliver s strange thoughts and life Blocks of the periodic table (s,p,d,f) electron configurations