- percentage composition always the same from sample to sample
- melt/boil at a characteristic temperature
- note: some compounds decompose before melting or boiling!
- two types
- not chemically decomposable into other elements
- properties do not vary
elements are made of atoms that all have the same atomic number
- obtaining elements from compounds involves chemical change
- electrolysis decomposes some compounds into elements
- some elements displace others from compounds
- writing element symbols
- first 1-2 distinguishing letters in name used for symbol
- only the first letter is uppercase!
- memorize symbols derived from ancient names:
Table 11 element symbols derived from ancient names.
|English name ||symbol ||ancient name |
|antimony ||Sb ||stibium|
|copper ||Cu ||cuprum |
|gold ||Au ||aurum|
|iron ||Fe ||ferrum |
|lead ||Pb ||plumbum|
|mercury ||Hg ||hydrargyrum |
|potassium ||K ||kalium|
|silver ||Ag ||argentum |
|sodium ||Na ||natrium|
|tin ||Sn ||stannum |
|tungsten ||W ||wolfram |
Classification of elements
- periodic table compactly shows relationships between elements
- features of the periodic table
- Periods are horizontal rows on the table.
Groups (or families) are columns on the table.
- elements in the same group are called congeners. They have similar chemical properties.
Blocks are regions on the table.
- important groups:
- alkali metals (Group IA, first column )
- soft, extremely reactive metals
- react with cold water to form hydrogen gas
- form +1 ions
- alkaline earth metals (Group IIA, second column):
- soft, reactive metals
- compounds are a major component of earth's crust
- form +2 ions
- halogens (Group VIIA, next-to-last column):
- poisonous and extremely reactive nonmetals
- fluorine and chlorine are yellow-green gases
- bromine is a volatile red-brown liquid
- iodine is a volatile blue black solid
- all form -1 ions
- noble gases (Group 0, last column)
- all are
- a. k. a. inert gases; almost completely unreactive
- Important blocks:
- transition metals are the elements in the region from the third to twelfth columns.
- hard, dense metals
- less reactive than Group IA and IIA
rare earth metals are the elements in the annex at the bottom of the table.
- lanthanides (annex, top row)
- actinides (annex, bottom row)
main group elements are all elements except the transition and rare earth metals.
- group numbers end with "A"
- metallic properties
malleability: can be hammered into thin sheets
ductility: can be drawn into wire
- conduct heat and electricity well
- one element can occur in several different forms ( allotropes)
Common allotropes of oxygen and carbon. The most stable form at room temperature and pressure is shown in boldface.
||O, nascent oxygen
||O2, oxygen gas
- gaseous elements commonly occur as diatomic molecules (except for the noble gases)
- percentage composition varies from sample to sample
- components are chemically different and retain properties in a mixture
- do not melt/boil at a definite temperature
- two types
- heterogeneous mixtures
- components not uniformly mixed
- more than one phase
- homogeneous mixtures
- components uniformly mixed
- one phase
- also called solutions
|How separation technology was used to solve a deadly mystery||
- mixture's components have different properties
- devise a process that selects components with certain properties
- density, melting point, boiling point, solubility, reactivity, magnetism, polarity
- some basic techniques
- filtration: select components by particle size
- floatation: select components by density
- crystallization: select components by solubility
- extraction: select components by solubility
- distillation: select components by boiling point
- chromatography: select components by affinity for a 'stationary phase'
General Chemistry Online! Matter
Copyright © 1997-2005 by Fred Senese
Comments & questions to email@example.com
Last Revised 07/25/05.URL: http://antoine.frostburg.edu/chem/senese/101/matter/print-index.shtml