|
|
עמוד:27
The alkali metals group The alkali metals are the metals in Column 1 of the periodic table ( except for hydrogen , which is also in Column 1 but does not belong to this group ) . The alkali metals are solid , soft and shiny-silvery . They are good electricity conductors and they are very chemically active – they combine easily with other materials . For this reason , the alkali metals do not occur naturally in their pure form . Instead , they occur as compounds with other elements . The alkali metals react with oxygen in the air , and they react quickly ( and sometimes very forcefully ) with water , a reaction in which hydrogen is emitted . The halogens group The halogens are the elements in Column 7 of the periodic table . The halogens are a family of colorful , toxic non-metal elements , consisting of diatomic molecules ( molecules consisting with two atoms ) . The halogens are highly chemically active – they tend to combine easily with other elements . The name halogen ( from Greek : Halo – salt , Gen – creator ) indicates their high degree of activity . The halogens do not naturally occur as separate elements . Instead , they occur as compounds with other elements , for example with metals from the alkali metals group . Such compounds are called salts . The halogens are the only group in which it is possible to find elements in all three states at room temperature : solid ( iodine and astatine ) , liquid ( bromine ) and gas ( chlorine , fluorine ) . Lithium and sodium salts are used to produce the red and yellow colors in fireworks . Sodium is an alkali metal . Chlorine is a halogen .
|
|