Developing the Periodic Table

Transcription

1 Developing the Periodic Table

2 Early Element Classification

3 Mendeleev s First Periodic Table

4 Mendeleev s First Periodic Table

5 Mendeleev s Periodic Table Arranged by increasing atomic mass Some elements did not follow the trend, why? Their atomic numbers were in different orders than their atomic masses Modern periodic tables are arranged by atomic number, why did Mendeleev arrange his by atomic mass? Rutherford discovered the nucleus in 1911, 40 years after Mendeleev first arranged the elements Grouped by properties Fluorine, Chlorine, Bromine, and Iodine were all placed into the same group because they had similar properties and bonded with other elements in the same ratios

6 Adding to Mendeleev In 1894, the gas argon (Ar) was discovered by John William Strutt and Sir William Ramsay The next year, the gas helium (He) was proven to exist on earth Sir Ramsay proposed a new group, the noble gases, be added to the periodic table Krypton (Kr), xenon (Xe), and radon (Rn) were all added to the noble gases as they were discovered

7 Modern Periodic Table Arranged by increasing atomic number A vertical column, known as a group contain elements with similar properties A horizontal row, known as a period, adds an energy level to the atom for each row

8 Group 1 - The Alkali Metals Have one valence electron Soft and silvery in color Metals which are good conductors of heat and electricity Low densities, low boiling points, low melting points React violently with water X

9 Group 2 - The Alkaline Earth Metals Have two valence electrons Are lustrous and silvery-white Are somewhat reactive React with water to form hydroxides which are basic X

10 Groups 3-12 Transition Metals Have various numbers of valence electrons We indicate the charges of their ions with Roman numerals Iron (IV) = Fe 4+ Copper (II) = Cu 2+ Are less reactive than alkali metals

11 Group 17 or 7A - The Halogens Have seven valence electrons Very good at stealing an electron from other compounds which make them great oxidizers Known as halogens because they react with metals to create salts At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid X

12 Group 18 or 8A - The Noble Gases Have full valence energy levels Are inert (unreactive) because they are so stable Gases at room temperature He X

13 Metals, Metalloids, and Nonmetals Metalloids: Boron Silicon Germanium Arsenic Antimony Tellurium Polonium Metals = Left Nonmetals = Right + Hydrogen

14 Diatomic Elements Some elements form diatomic (two atoms) molecules in their elemental form. These include: Hydrogen Nitrogen Oxygen Fluorine Chlorine Bromine Iodine

15 Oxidation Numbers The oxidation number is the charge that an ion of a group in the periodic table will usually have. Write these on your white periodic table

16 Oxidation Numbers Oxidation numbers are related to the number of valence electrons Valence electrons are the number of electrons in the outermost energy level of an atom The Roman numerals next to the As in the column heading tell how many valence electrons are in that group

17 Practice Which element is in group 2 and period 7 of the periodic table? Which element is in group 3A and period 3 of the periodic table? Which element is in group 18 and period 1 of the periodic table?

18 Practice Which set of elements contains a metalloid? A. K, Mn, As, Ar B. Li, Mg, Ca, Kr C. Ba, Ag, Sn, Xe D. Fr, F, O, Rn

19 Practice The most reactive family of metals is the A. Transition metals B. Alkaline earth metals C. Alkali metals Which of the following is most likely to have similar properties to calcium? A. Potassium B. Barium C. Scandium

20 Practice Which of the following is most likely to have an ion with a charge of +3? A. Sodium B. Aluminum C. Silicon Which of the following is most likely to have an ion with a charge of -2? A. Fluorine B. Krypton C. Oxygen

21 Practice Name a main group element with 6 valence electrons. Name a main group element with 1 valence electron. Name a main group element with 3 valence electrons.

22 Practice: Average Atomic Mass Find the average atomic mass of chlorine given 35 Cl is 75.77% abundant and 37 Cl is 24.23% abundant. Find the average atomic mass of iodine given 127 I is 80% abundant, 126 I is 17% abundant, and 128 I is 3% abundant.