Metals
Page 1 of 1
Metals
Ian Mon May 19, 2008 10:10 am
Metal
In chemistry, a metal (Greek: Metallon) is defined as an element that readily loses electrons to form positive ions (cations) and forms metallic bonds between other metal atoms. (forming ionic bonds with non-metals). In common usage, the term "metal" is also used to describe something that is considered to be strong, tough, or heavy-duty, without necessarily indicating that the object in question is actually made of metal elements (as in heavy metal music).
chemical property
Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over changing timescales (iron rusts over years, while potassium burns in seconds).
physical rpoperty
Metals in general have superior electric and thermal conductivity, high luster and density, and the ability to be deformed under stress without cleaving. While there are several metals that have low density, hardness, and melting points, these (the alkali and alkaline earth metals) are extremely reactive, and are rarely encountered in their elemental, metallic form.
The alkali metals are the most volatile, followed by the alkaline earth metals, found in the leftmost two groups of the periodic table.
The transition metals (such as iron, copper, zinc, and nickel) take much longer to oxidize. Others, like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades (like aluminium, some steels, and titanium). The oxides of metals are basic (as opposed to those of nonmetals, which are acidic), although this may be considered a rule of thumb, rather than a fact.
Alkali metals
The alkali metals are the series of elements in Group 1 of the periodic table (excluding hydrogen in all but one rare circumstance): lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
Alkaline earth metals
The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well characterized homologous behavior down the group.”
The alkaline earth metals are silvered colored, soft metals, which react readily with halogens to form ionic salts, and with water, though not as rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. For example, where sodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium with hot water
Transition metals
The term transition metal has two possible meanings:
1. It commonly refers to any element in the d-block of the periodic table, excluding zinc, cadmium and mercury. This corresponds to groups 3 to 12 on the periodic table.
2. More strictly, IUPAC defines a transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." By this definition, zinc, cadmium, and mercury are excluded from the transition metals, as they have a d10 configuration. Only a few transient species of these elements that leave ions with a partly filled d subshell have been formed, and mercury(I) only occurs as Hg22+, which does not strictly form a lone ion with a partly filled subshell, and hence these three elements are inconsistent with the latter definition.[1] They do form ions with a 2+ oxidation state, but these retain the 4d10 configuration. Element 112 may also be excluded although its oxidation properties are unlikely to be observed due to its radioactive nature. This definition corresponds to groups 3 to 11 on the periodic table.
In chemistry, a metal (Greek: Metallon) is defined as an element that readily loses electrons to form positive ions (cations) and forms metallic bonds between other metal atoms. (forming ionic bonds with non-metals). In common usage, the term "metal" is also used to describe something that is considered to be strong, tough, or heavy-duty, without necessarily indicating that the object in question is actually made of metal elements (as in heavy metal music).
chemical property
Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over changing timescales (iron rusts over years, while potassium burns in seconds).
physical rpoperty
Metals in general have superior electric and thermal conductivity, high luster and density, and the ability to be deformed under stress without cleaving. While there are several metals that have low density, hardness, and melting points, these (the alkali and alkaline earth metals) are extremely reactive, and are rarely encountered in their elemental, metallic form.
The alkali metals are the most volatile, followed by the alkaline earth metals, found in the leftmost two groups of the periodic table.
The transition metals (such as iron, copper, zinc, and nickel) take much longer to oxidize. Others, like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades (like aluminium, some steels, and titanium). The oxides of metals are basic (as opposed to those of nonmetals, which are acidic), although this may be considered a rule of thumb, rather than a fact.
Alkali metals
The alkali metals are the series of elements in Group 1 of the periodic table (excluding hydrogen in all but one rare circumstance): lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
Alkaline earth metals
The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well characterized homologous behavior down the group.”
The alkaline earth metals are silvered colored, soft metals, which react readily with halogens to form ionic salts, and with water, though not as rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. For example, where sodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium with hot water
Transition metals
The term transition metal has two possible meanings:
1. It commonly refers to any element in the d-block of the periodic table, excluding zinc, cadmium and mercury. This corresponds to groups 3 to 12 on the periodic table.
2. More strictly, IUPAC defines a transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." By this definition, zinc, cadmium, and mercury are excluded from the transition metals, as they have a d10 configuration. Only a few transient species of these elements that leave ions with a partly filled d subshell have been formed, and mercury(I) only occurs as Hg22+, which does not strictly form a lone ion with a partly filled subshell, and hence these three elements are inconsistent with the latter definition.[1] They do form ions with a 2+ oxidation state, but these retain the 4d10 configuration. Element 112 may also be excluded although its oxidation properties are unlikely to be observed due to its radioactive nature. This definition corresponds to groups 3 to 11 on the periodic table.
Ian- Posts : 7
Join date : 2008-01-05
Page 1 of 1
Permissions in this forum:
You cannot reply to topics in this forum|
|
|