Chemistry

The Alkaline Earth Metals of Group 2



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The Alkaline Earth metals form Group 2 of the Periodic table. Group 2 is the International Union for Pure and Applied Chemistry (IUPAC) preferred nomenclature but other versions of the table may use 2A or IIA. The seven elements forming the alkaline earth metal group are beryllium (Be, atomic number 4), magnesium (Mg, 12), calcium (Ca, 20), strontium (Sr, 38), barium (Ba, 56) and radium (Ra, 88). They are all silver/white shiny metallic elements.

Together with the Alkali metals of Group 1, the alkaline earth metals form the s-block of elements. This refers to the electron s-sub-shell. S-sub-shells contain only two electrons and in members of the s-block, the outer most electron sub-shell containing any electron is the s-sub shell.

When forming ions an element either donates or receives one or more electrons. The name alkaline earth comes from their oxides, which dissolve to form an alkaline solution but do not burn in fire. Alchemists gave the name earth to compounds that did not burn.

The metals are all highly reactive but not as reactive as the alkali metal group. Because they are reactive, alkaline earth metals do not occur in their pure state in nature but compounds containing them occur in many minerals.

All the isotopes of radium are extremely radioactive but the other members of the group each have at least one stable isotope. The danger radium poses, as a source of radioactive poisoning is great. One gram of radium emits about a million times the radioactivity as an equivalent amount of uranium. Because of its inherent danger, the chemical reactions of this element are not well studied.

Elements donating electrons to form ions are referred to as reducing agents while those receiving electrons are oxidizing agents. All the alkaline earth metals are reducing agents. The two electrons within the outer s-sub shell (known as valence electrons) are donated in forming ionic compounds.

Alkaline earth element’s reactions with such elements as oxygen and chlorine become more vigorous as their atomic number increases. All except beryllium form oxides on exposure to air at normal room temperature. The reaction of barium with atmospheric oxygen is so extreme that pure samples of the metal require storage under mineral oil.

All the alkaline earth metals are reducing agents. Their reaction with such elements as oxygen and chorine become more vigorous as their atomic number increases. All except barium form oxides on exposure to air at normal room temperature. The reaction of barium with atmospheric oxygen is so extreme that pure samples of the metal require storage under mineral oil.

The atomic radii of the elements increase as their atomic number increases. Their ionic radii are much smaller than their atomic radii as not only have they lost the outer two electrons, in the ionic state the remaining electrons are drawn closer to the positively charged nucleus.

Many of the metals produce a characteristic colored flame when the burn. These colors are calcium – brick-red, strontium – crimson, barium – apple-green and radium – carmine-red.



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