CHEM 140 Chapter Notes - Chapter 4: Mass Number, Weighted Arithmetic Mean, Unified Atomic Mass Unit

• School: CSULB
• Department: Chemistry and Biochemistry
• Course: CHEM 140
• Professor: P Pierce

Document Summary

Elements are pure substances from which all other things are built. Chemical symbols are one or two letter abbreviations for element names. 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. 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. 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. Most metals are shiny solids that can be hammered into a flat sheet.