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The group 2 elements’ tendency to oxidize is so strong that the metals of group 2 were all first detected in their oxide forms: beryl is beryllium oxide, magnesia is magnesium oxide, lime is calcium oxide, strontian is strontium oxide, and baryta was an old name for barium compounds with oxygen or sulfur. On the other hand, group 2 are called alkaline ‘earth’ metals because their oxides are less reactive than group 1. They have very low water solubilities and cannot normally be burned in air. As the table predicts, each alkaline earth metal’s s2 electron configuration means that they tend to form a plus two ion, combining in a one-to-one ratio with oxygen. It was this property that landed them in group 2 of Mendeleev’s table, long before their atomic structure was uncovered. Also, much like their group 1 neighbors, each element’s oxide or hydroxide and can be electrolyzed to obtain pure elemental metals—a technique that allowed Humphry Davy in the first decade of the 1800s to go on his famous tear of isolating new elements, including four of the alkaline earth metals.
Discovery of Magnesium and CalciumMagnesium and calcium were the first alkaline earth metals to be discovered. This is in part because their similarities lead to magnesium and calcium commonly accumulating together in nature. There is evidence that as far back as 4,000 years ago, ancient Mesopotamians used a very special substance that could be obtained by subjecting limestone to extreme heat in special kilns in a process called ‘calcining’’ By the 1600s and 1700s, this process became commonplace in the western hemisphere as a means of obtaining mortar for brick construction. Natural limestone itself is made of a mixture of calcium and magnesium carbonates, and heating these substances drives off carbon dioxide gas, leaving behind a combination of metal oxides of both metals, known then as quicklime. Surprising Features of Group 2 ElementsThe alkaline earth metals from group 2 all tend to form insoluble oxide compounds that react with water or acids to form bases. Just as we saw with sodium and potassium for the alkali metals, the row 3 and row 4 representatives from this group—magnesium and calcium—are by far the most abundant of their group. Their high concentrations in our environment have made them readily available to participate in the evolution of biological chemistry as well. The second column of the periodic table also has a few surprises. Beryllium’s universal abundance is shockingly low mostly because of its low nuclear binding energy, but its lithophilic characteristics have concentrated it in our Earth’s crust, making it available, and a valuable, material as a native metal because of its low density and its strength. On the other hand, its unusually strong bonds to oxygen—more akin to those made by its diagonal neighbor aluminum—make it difficult to access in a bioavailable form. This has left the human body with no way to manage beryllium if it finds a way inside us. Strontium and RadiumStrontium’s position just below calcium on the table accurately predicts that it can substitute for calcium in the body, making its radioactive isotopes particularly dangerous when they are released into our environment. We saw how barium’s name, literally meaning ‘heavy’, accurately describes the properties of some of its compounds, but falls short of describing its properties as a pure element. And the final element of the group is radium. Radium definitely lives up to its name, as its ionizing radiation led to both its most famous and infamous application—production of luminescent paints that were wildly popular, but proved so dangerous to work with that their use precipitated a new era in labor force protection law. Although every element is unique in its own way, the s-block elements shared a great deal in common with one another. Common Questions about Group 2 ElementsQ: How do group 1 and group 2 elements differ? Group 1 and group 2 elements have much in common. Still, since the group 2 elements have two valence electrons, they are less reactive to some extent, form stronger metallic bonds, have higher melting points, and their oxides are less reactive than group 1. These elements also hardly solve in water and can not be burned in air. Q: What are some features of magnesium and calcium? These two elements were the very first alkaline earth metals to be discovered. They are also the most abundant group 2 elements. Their abundance and availability have led to their inclusion in the development of biological chemistry. Q: What is one surprising trait of beryllium? Beryllium has a low universal abundance. This feature of this group 2 element of the periodic table is due to its low nuclear binding energy. However, due to its lithophilic properties, it is concentrated in the earth’s crust and is a valuable native metal because it is strong and dense. Keep ReadingThe Periodic Table: Discovery of the Elements in the First ColumnThe Fascinating Qualities of Alkali MetalsWhich Group 1 Metals Influence Our Everyday Lives?
In order to continue enjoying our site, we ask that you confirm your identity as a human. Thank you very much for your cooperation. A valence electron is an electron that is associated with an atom, and that can participate in the formation of a chemical bond; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair. The presence of valence electrons can determine the element's chemical properties and whether it may bond with other elements: For a main group element, a valence electron can only be in the outermost electron shell. An atom with a closed shell of valence electrons (corresponding to an electron configuration \(s^2p^6\)) tends to be chemically inert. An atom with one or two valence electrons more than a closed shell is highly reactive, because the extra valence electrons are easily removed to form a positive ion. An atom with one or two valence electrons fewer than a closed shell is also highly reactive, because of a tendency either to gain the missing valence electrons (thereby forming a negative ion), or to share valence electrons (thereby forming a covalent bond). Like an electron in an inner shell, a valence electron has the ability to absorb or release energy in the form of a photon. An energy gain can trigger an electron to move (jump) to an outer shell; this is known as atomic excitation. Or the electron can even break free from its associated atom's valence shell; this is ionization to form a positive ion. When an electron loses energy (thereby causing a photon to be emitted), then it can move to an inner shell which is not fully occupied. The number of valence electrons of an element can be determined by the periodic table group (vertical column) in which the element is categorized. With the exception of groups 3–12 (the transition metals), the units digit of the group number identifies how many valence electrons are associated with a neutral atom of an element listed under that particular column.
The periodic table of the chemical elements
* The general method for counting valence electrons is generally not useful for transition metals. Instead the modified d electron count method is used. ** Except for helium, which has only two valence electrons.
The valence (or valency) of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. The concept of valence was developed in the last half of the 19th century and was successful in explaining the molecular structure of many organic compounds. The quest for the underlying causes of valence lead to the modern theories of chemical bonding, including Lewis structures (1916), valence bond theory (1927), molecular orbitals (1928), valence shell electron pair repulsion theory (1958) and all the advanced methods of quantum chemistry. The combining power or affinity of an atom of an element was determined by the number of hydrogen atoms that it combined with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, oxygen has a valence of two; and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen, so phosphorus has a valence of 5 in phosphorus pentachloride, PCl5. Valence diagrams of a compound represent the connectivity of the elements, lines between two elements, sometimes called bonds, represented a saturated valency for each element.[1] Examples are:-
Valence only describes connectivity, it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. The line between atoms does not represent a pair of electrons as it does in Lewis diagrams.
Khan Academy Valence Electrons Cliffs Notes Valence Electrons Contributors |
Group 2 elements have two valence electrons which kind of bond will they most likely form, and why
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