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Periodicity Glencoe Chapter 6. phabetic.htm phabetic.htm.

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Presentation on theme: "Periodicity Glencoe Chapter 6. phabetic.htm phabetic.htm."— Presentation transcript:

1 Periodicity Glencoe Chapter 6

2 phabetic.htm phabetic.htm

3 Development of the Modern Periodic Table 1790s – 23 known elements By 1870s – 70 known elements John Newlands proposed arrangements by mass and properties by octaves 1864 – Lothar Meyer proposes arrangements by mass and columns of propertiesbut doesnt publish! 1869 – Dmitri Mendeleev also proposed arrangements by mass and columns of propertiesand announces! 1913 – Henry Moseley proposed arrangements by atomic number. (periodic law) 1913 – Henry Moseley proposed arrangements by atomic number. (periodic law)

4 Newlands octaves H 1F 8Cl 15Co/Ni 22Br 29Pd 36I 42Pt/Ir 50 Li 2Na 9K 16Cu 23Rb 30Ag 37Cs 44Tl 53 Gl 3Mg 10Ca 17Zn 25Sr 31Cd 34Ba/V 45Pb 54 Bo 4Al 11Cr 18Y 24Ce/La 33U 40Ta 46Th 56 C 5Si 12Ti 19In 26Zr 32Sn 39W 47Hg 52 N 6P 13Mn 20As 27Di/Mo 34Sb 41Nb 48Bi 55 O 7S 14Fe 21Se 28Ro/Ru 35Te 43Au 49Os 51

5 Shortly after, his ideas were presented to the Russian Physico-chemical Society. They were read by Professor Menschutkin because Mendeleev was ill. His ideas were then published in the main German chemistry periodical of the time, Zeitschrift fϋr Chemie. The worlds first view of Mendeleevs Periodic Table – an extract from Zeitschrift fϋr Chemie, Click here for a translation

6 Key landmarks of the modern periodic table Periods (horizontal) Groups/families (vertical) Representative elements s & p block s & p block Groups 1A – 8A Groups 1A – 8A Groups 1,2,13,14,15,16,17,18 Groups 1,2,13,14,15,16,17,18 Transition elements d block (f block = inner transition elements) d block (f block = inner transition elements) Groups 1B – 8B Groups 1B – 8B Groups Groups

7 Other notable classifications: Metals Alkali (group 1) Alkali (group 1) Alkaline (group 2) Alkaline (group 2)MetalloidsNonmetals Halogens (group 17) Halogens (group 17) Noble gases (group 18) Noble gases (group 18)

8 Periodic trends Vary systemically across a period (horizontally) across a period (horizontally) down a group (vertically) down a group (vertically)

9 Atomic radii Based on probability of electron cloud, therefore, defined by how closely an atom lies to a neighboring atom DECREASES to the right across a period Due to larger nuclear attraction Due to larger nuclear attraction INCREASES down a group Due to more layers of electrons Due to more layers of electrons

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11 Ionic Radii Ions (charged atoms) form when electrons are gained or lost….(the number of protons and electrons dont match!) DECREASES to the right across a period (in two phases) INCREASES down a group

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13 Ionization Energy Defined as amount of energy required to remove an electron from a gaseous atom 1 st ionization energy 1 st ionization energy 2 nd ionization energy 2 nd ionization energy Etc. Etc. Think of this as the atoms ability to hold onto its valence electron! INCREASES across a period Harder to remove e- Harder to remove e- Positive energy means harder Positive energy means harder DECREASES down a group Easier to remove e- Easier to remove e- More negative energy means easier or more stable More negative energy means easier or more stable

14 ElementI1I2I3I4I5I6I7 Na Mg Al ,600 Si ,100 P ,200

15 Octet Rule Atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons Note chemical stability of noble gases Note chemical stability of noble gases Predicts ionic charge of main block elements Predicts ionic charge of main block elements CATIONSpositively charged ions (lost e-) ANIONSnegatively charged ions (gained e-)

16 Electron Affinity Energy associated with adding an electron to an atoms electron cloud---think of the opposite of Ionization Energy…but same effect! INCREASES (but the energy gets more negative = means more stable) across period DECREASES (but the energy value gets more positive = means more difficult) down group Therefore, a great idea!....

17 Electronegativity Indication of the relative ability of the atom to attract electrons in a chemical bond Think of this quantity as how strongly an atom might want to gain an electron. Think of this quantity as how strongly an atom might want to gain an electron. Arbitrary rating scaled to 4.0….. Most electronegative element is fluorine with 3.98 Most electronegative element is fluorine with 3.98 INCREASES across a period DECREASES down a group

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19 Summary of Trends


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