CHEM 140 Chapter 4: Chem 140- chapter 4

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Chemistry and Biochemistry
CHEM 140
P Pierce

Chem 140 Chapter 4 notes Atoms and Elements Heading: Notes: Elements and Symbols ● Elements are pure substances from which all other things are built ● Chemical symbols are one or two letter abbreviations for element names The Periodic Table ● Each horizontal row in the periodic table is a period: counted from top to bottom as periods 1-7 ● Each vertical column contains a group that has similar properties ● The representative elements have groups from 1A to 8A ● Transition elements have group letters B ● Numbers 1-18 are also used to assign groups b ● Group 1A are alkali metals are they are soft shiny metals that can conduct heat and electricity well. Have low melting points and react vigorously with water and when combined with O2, form white products. ● Hydrogen is not an alkali metal ● 2A, alkaline earth metals are shiny but not reactive ● Halogens, 7A, are highly reactive and form compounds with most elements ● Noble gases, 8A, are unreactive and do not combine with other elements Metals, Nonmetals, and metalloids ● Most metals are shiny solids that can be hammered into a flat sheet. They make good conductors of heat and electricity, melt at highter temperatures than nonmetals. Located in B group ● All metals are solid at room temperature except for mercury ● Nonmetals not really shiny malleable and not great conductos. located to the right of the zig zag line. Have low melting points and densities ● Metalloids are located on the zig zag line. They have some properties of metals and some properties of nonmetals. Better conductors, but still not as good as metals-semiconductors. Can be modified to conduct or insulate The Atom ● An atom is the smallest particle of an element that retains the characteristics of an element ● John Dalton discovered the atom by figuri
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