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The Ultimate Cheat-Sheet

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Presentation on theme: "The Ultimate Cheat-Sheet"— Presentation transcript:

1 The Ultimate Cheat-Sheet
The Periodic Table The Ultimate Cheat-Sheet

2 Elementary My Dear Watson….
Elements are distinguished by the number of protons Each element has unique properties How are they arranged? Is there a pattern?

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4 The “Original”

5 Why Do We Need a Periodic Table?
By 1700, only 13 elements were known The rate of discovery increased in the 18th century (Davy, Lavoisier, Priestly) But how could scientists know an element was “new?” Chemists needed a way to organize the elements

6 How Was It Developed? In 1829, Dobereiner published a classification system using triads Triads are groups of 3 elements with similar properties But, not all elements could be grouped into triads

7 Lothar Meyer In 1864, Lothar Meyer published an early version of the periodic table It contained 28 elements classified into 6 families by their valence (combining power) This was the first time that elements had been grouped and ordered according to their valence. Work on organizing the elements by atomic weight had hitherto been stymied by inaccurate measurements of the atomic weights.

8 de Chancourtois One of the first to notice periodicity
In 1862 developed a cylindrical design Ignored due to “geological terms”

9 How Was It Developed…. In 1865, Newlands classified elements into 11 groups Noticed that many groups differed by “8” He called this his “Law of Octaves”

10 Development Other systems were explored…
In 1869, Dmitri Mendeleev proposed his periodic table He played “chemical solitaire” on the train There were 60 elements to organize

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12 How Did Mendeleev Do It? He organized the elements by increasing atomic mass and “combining power” He left a space in his table if an element was unknown In time, those spaces were filled in with elements that matched his predictions

13 Elements’ Properties are Predicted
Property Mendeleev’s Predictions in 1871 Observed Properties Molar Mass Oxide formula Density of oxide Solubility of oxide Scandium (Discovered in 1877) 44 g M2O3 3.5 g / ml Dissolves in acids 43.7 g Sc2O3 3.86 g / ml Molar mass Density of metal Melting temperature Gallium (Discovered in 1875) 68 g 6.0 g / ml Low Dissolves in ammonia solution 69.4 g 5.96 g / ml 30 0C Ga2O3 Dissolves in ammonia Color of metal Chloride formula Density of chloride Boiling temperature of chloride Germanium (Discovered in 1886) 72 g 5.5 g / ml Dark gray High MO2 4.7 g / ml MCl4 1.9 g / ml Below 100 oC 71.9 g 5.47 g / ml Grayish, white 900 0C GeO2 4.70 g / ml GeCl4 1.89 g / ml 86 0C Fitting in New Elements “The crowning achievement of Mendeleyev’s periodic table lay in his prophecy of new elements. Gallium, germanium, and scandium were unknown in 1871, but Mendeleyev left spaces for them and even predicted what the atomic masses and other chemical properties would be. The first of these to be discovered in 1875, was gallium. All the characteristics fitted those he had predicted for the elements Mendeleyev called eka-aluminum – because it came below aluminum in his table.” -Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 23 In the 1860’s, Mendeleev and the German chemist Lothar Meyer, each working alone, made an eight-column table of the elements. However, Mendeleev had to leave some blank spots in order to group all the elements with similar properties in the same column. To explain these blank spots, Mendeleev suggested there must be other elements that had not yet been discovered. On the basis of his arrangement, Mendeleev predicted the properties and atomic masses of several elements that were unknown at the time. Mendeleev left blanks in his table for undiscovered elements. Mendeleev predicted properties and masses of unknown elements correctly. O’Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 119,

14 Mendeleev Some people consider Meyer and Mendeleev the co-creators of the periodic table Most agree that Mendeleev's accurate prediction of the qualities of what he called eka-silicon (germanium), eka-aluminium (gallium) and eka-boron (scandium) qualifies him for deserving the majority of the credit for studies

15 Mendeleev did not know the structure of atoms and that the number of protons was unique for each element Now the periodic table is arranged by increasing atomic number

16 The Modern Periodic Table
Is an organized display of elements Is arranged so that elements with similar properties fall into the same group Is used to predict the behavior of elements The “Noble Gases” don’t easily react with other elements.

17 Rows of the Periodic Table
Rows of the PT are called “periods.” All of the elements in a period have the same number of energy levels for their valence (s & p) electrons

18 K and Kr are very different
Periods (cont.) Elements close to each other in the same period are more similar than those further away. K and Ca are similar K and Kr are very different

19 So… Properties of the elements within a period change as we move across a period from left to right The pattern of properties within a period repeats as we move from one period to the next

20 The Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

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22 Regions of the PT

23 1) Metals The largest region of the PT ~ 80%

24 Properties of Metals Excellent conductors of heat and electricity
Usually lustrous, ductile, and malleable. Gold charm Sodium metal Copper wire

25 2) Nonmetals The second largest region of the PT

26 Properties of Nonmetals
Poor conductors of heat and electricity Most are gases or brittle solids at room temperature. Chlorine gas Graphite Diamond

27 3) Metalloids Have some properties of metals and some of nonmetals
Silicon is useful in computers because they conduct electricity “moderately” Semi-conductors

28 Other Uses of Metalloids
Lasers Infrared sensors Alloys Glass products Added Impurities

29 The Elements at the Bottom
These are the lanthanides and actinides Glenn Seaborg “moved” these

30 Special Groups of Elements
Group 1A – the Alkali Metals The name alkali comes from the Arabic al aqali, meaning “the ashes.” Wood ashes are rich in compounds containing sodium and potassium Group 2A – the Alkaline Earth Metals Group 7A – the Halogens Literally means “salt former”

31 The Representative Elements
These are the elements in Groups 1A – 7A They represent a wide range of properties Metals, nonmetals, and metalloids Solids, liquid (Br), and gases The highest level s & p orbitals are NOT filled

32 Examples Electron configurations for Group 1A

33 Group Number and e- Number
For any representative element, its group number equals the number of electrons in the highest occupied energy level (valence electrons). Group 1A Group 4A

34 Noble Gases NOT considered representative elements Unreactive Uses:
Krypton is mixed with Argon in fluorescent lights (also to render Superman inert) Neon is used for signs Helium is used in weather and toy balloons

35 What About The “Ones in the Middle”
These have different letter designations, depending on the table These are also called Transition metals Inner transition metals

36 Transition Metals The highest occupied s sublevel and a nearby d sublevel contain electrons These elements are also called d -block elements

37 The Inner Transition Metals
AKA: the lanthanides and actinides. The highest occupied s sublevel and a nearby f sublevel generally contain electrons.

38 f-orbitals

39 Blocks of Elements

40 Rare Earth Elements Scandium, Yttrium, Lanthanum, and Cerium through Lutetium Used in electronics Thulium (Tm) – lasers & x-rays Neodymium (Nd) - magnets Not rare – hard to separate Elements very similar Charges are 3+

41 The Racetrack Design


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