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Lecture 8

CHEM H90 Lecture 8: A Brief Introduction to the Elements (04/18/17)

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LECTURE 8 Wednesday, April 19, 2017 Conversion using moles How much does a mole of methane weigh? o Chemical formula CH 4 o Atomic masses: C is 12, H is 1, so one CH we4ghs 16 amu o 1 mole is molecular weight expressed in g o So 1 mole of CH we4ghs 16g How many protons in 1 g of CH ?4 o 1 mole has 6 x 10 molecules 24 o Each molecule has 10 protons, so 1 mole has 6 x 10 protons o So 1 g has 6 x 10 16 protons A Brief Introduction to the Elements Modern Periodic Table As you go down a column, it indicates similar chemical properties because the valence electron configurations are the same (1s, 2s, 1p, etc.) Trends in Reactivity An important feature is this diagonal of metalloids o The biggest separation is between metals and nonmetals o The physical features change from gases on top to metals on the bottom Elements in the same group resemble each other because they have the same outer electron configuration. But Groups IIIA, IVA, VA, and VIA have more diversity because they include metals, nonmetals, and metalloids Hydrogen Electron configuration: 1s1 + Forms H ion (proton) and H ion (hydride) Exists as a diatomic molecule, H2(gas) Not a metal o But if you put it under enough pressure, people believe that it will turn into a metal. This is important for the interiors of gas giants. Metallic hydrogen is predicted to exist at very high pressures However, researchers at CEA in France have shown that it is still not metal at 100 K and 3.2 million atmospheres. This is close to the pressure at the center of the earth. Alkali metals (group IA) These are the lefthand side elements with similar properties Electron configuration: [x]ns , n 2
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