Chemistry
Group 2 Alkaline Metals
Group 2 alkaline metals are a set of metallic elements in the periodic table, including beryllium, magnesium, calcium, strontium, barium, and radium. They are known for their high reactivity and tendency to form 2+ cations. These metals are typically found in compounds rather than in their pure form and are important in various industrial and biological processes.
Written by Perlego with AI-assistance
Related key terms
1 of 5
10 Key excerpts on "Group 2 Alkaline Metals"
eBook - ePubEssentials of Inorganic Chemistry
For Students of Pharmacy, Pharmaceutical Sciences and Medicinal Chemistry
- Katja A. Strohfeldt(Author)
- 2015(Publication Date)
- Wiley(Publisher)
Chapter 3 Alkaline Earth MetalsMembers of group 2 of the periodic table (second vertical column) are calledearth alkaline metals. In this group are included the following elements: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Radium is a radioactive element and therefore we will not further discuss it in this chapter (Figure 3.1 ).Periodic table of elements; group 2 elements are highlightedFigure 3.1In terms of clinical use, magnesium and calcium are essential ions for the human body and any of their imbalances should be corrected. Strontium is medically used in radiotherapy, and its application is further discussed in Chapter 10. Exposure to excess beryllium can lead to the so-called chronic beryllium disease (CBD), which is discussed later in this chapter. Barium salts are generally highly toxic. Nevertheless, the so-called barium meal is a well-used oral radio-contrast agent.3.1 Earth alkaline metal ions
Earth alkaline metals together with the alkali metals form the so-called s-block metals. Earth alkaline metals have two electrons in their outer shell which is an s-orbital type. The chemistry of the metals is characterised by the loss of both electrons, which is a result of the relatively low ionisation energy (IE) of both electrons and the subsequent formation of the stable cation M2+ , which has a noble gas configuration (Table 3.1 ).Source: Reproduced with permission from [8]. Copyright © 1996, John Wiley & Sons, Ltd.First, second and third ionisation energies (kJ/mol) of group 2 metals [1]Table 3.1First Second Third Be 900 1 757 14 847 Mg 738 1 450 7 731 Ca 590 1 145 4 910 Sr 550 1 064 4 207 Ba 503 965 3 600 Group 2 elements are all silvery-white metals with high reactivity, similar to alkali metals, but less soft and not as reactive. Earth alkaline metals can be mostly found in the earth's crust in the form of their cations displayed in minerals and not as the elemental metal, as these are very reactive. For example, beryllium principally occurs as beryl (Be3 Al2 [Si6 O18 ]), which is also known asaquamarine
eBook - PDF- Bernard Moody(Author)
- 2013(Publication Date)
- Arnold(Publisher)
18 Group II: the alkaline-earth metals Beryllium, magnesium, calcium, strontium and barium The alkaline-earths are a family of very reactive metals in which the electro-positive nature increases sharply with increase in atomic number. Calcium, strontium, bar-ium and radium form a close series of very similar ele-ments and compounds with a steady gradation of proper-ties. Radium, isolated by the Curies in 1898 from pitch-blende, a mineral of uran-ium which showed unex-pectedly high radioactivity, is highly radioactive and while those salts which have been studied show the nor-mal alkaline-earth characteristics, neither the ele-ment nor its compounds will be described further here. Magnesium is somewhat apart from metals which follow it, showing some resemblance to zinc, which heads the other subgroup assigned to Group II. Magnesium and calcium compounds in general use are described in detail as are a few compounds of barium. Strontium and its salts are compara-tively rare. Some compounds of strontium and barium are mentioned to reveal their overall similarity to the corresponding compounds of calcium. Beryllium is very distinctive; it differs from magnesium more than that element differs from the others, and while it undoubtedly belongs to Group II, it resembles the diagonally placed element, aluminium, so much that at one time beryllium was considered to be tervalent. The metals magnesium, calcium, strontium and barium are white, lustrous when freshly exposed but quickly tarnished by the atmosphere, and fairly soft. Barium is usually stored in oil and when finely divided is spontaneously flammable. The melting-points and boiling-points do not follow a regular pattern, while the densities at room temperature decrease from beryllium to calcium and then rise to barium. This is accounted for by differences in crystal structure.
eBook - PDFEssentials of Inorganic Chemistry
For Students of Pharmacy, Pharmaceutical Sciences and Medicinal Chemistry
- Katja A. Strohfeldt(Author)
- 2014(Publication Date)
- Wiley(Publisher)
3 Alkaline Earth Metals Members of group 2 of the periodic table (second vertical column) are called earth alkaline metals. In this group are included the following elements: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Radium is a radioactive element and therefore we will not further discuss it in this chapter (Figure 3.1). In terms of clinical use, magnesium and calcium are essential ions for the human body and any of their imbalances should be corrected. Strontium is medically used in radiotherapy, and its application is further discussed in Chapter 10. Exposure to excess beryllium can lead to the so-called chronic beryllium disease (CBD), which is discussed later in this chapter. Barium salts are generally highly toxic. Nevertheless, the so-called barium meal is a well-used oral radio-contrast agent. 3.1 Earth alkaline metal ions Earth alkaline metals together with the alkali metals form the so-called s-block metals. Earth alkaline metals have two electrons in their outer shell which is an s-orbital type. The chemistry of the metals is characterised by the loss of both electrons, which is a result of the relatively low ionisation energy (IE) of both electrons and the subsequent formation of the stable cation M 2+ , which has a noble gas configuration (Table 3.1). Group 2 elements are all silvery-white metals with high reactivity, similar to alkali metals, but less soft and not as reactive. Earth alkaline metals can be mostly found in the earth’s crust in the form of their cations displayed in minerals and not as the elemental metal, as these are very reactive. For example, beryllium principally occurs as beryl (Be 3 Al 2 [Si 6 O 18 ]), which is also known as aquamarine. Magnesium can be found in rock structures such as magnesite (MgCO 3 ) and dolomite (MgCO 3 ⋅CaCO 3 ), and is the eighth most abundant element in the earth’s crust.
eBook - ePub- Richard C. Ropp(Author)
- 2012(Publication Date)
- Elsevier(Publisher)
Chapter 1 The Alkaline Earths as Metals Outline1.1. General Properties1.2. Properties of the Alkaline Earth Metals1.2.1. Beryllium1.2.2. Magnesium1.2.3. Calcium1.2.4. Strontium1.2.5. Barium1.2.6. RadiumThe alkaline earth metals comprise Group 2 of the periodic table and include the elements Be, Mg, Ca, Sr, Ba and Ra. These metals form cations with a formal charge of +2 in solution and are the second most electropositive metals of all of the elements (the alkali metals are the most electropositive). The name of this specific group in the periodic table stems from the fact that their oxides produce basic alkaline solutions and that these elements melt at such high temperatures that they remain solid (earths) in fires. The alkaline earth metals provide a good example of group trends in chemical properties within the periodic table, with well-characterized homologous behavior as one goes down the group. With the exception of Be and Mg, the metals have a distinguishable flame color, orange-red for Ca, magenta-red for Sr, green for Ba and crimson-red for Ra.1.1 General Properties
Like other groups, the members of this family show specific patterns in their electron configuration, especially the outermost shells, that results in trends in chemical behavior (Table 1.1 ).TABLE 1.1Z Element No. of electrons/shell 4 Beryllium 2, 2 12 Magnesium 2, 8, 2 20 Calcium 2, 8, 8, 2 38 Strontium 2, 8, 18, 8, 2 56 Barium 2, 8, 18, 18, 8, 2 88 Radium 2, 8, 18, 32, 18, 8, 2 Another way to depict the electronic structure of these elements is shown in Table 1.2 .TABLE 1.2Element Symbol Electronic configuration Beryllium Be [He]2s2 Magnesium Mg [Ne]3s2 Calcium Ca [Ar]4s2 Strontium Sr [Kr]5s2 Barium Ba [Xe]6s2 Radium Ra [Rn]7s2 All of the alkaline earth metals have two electrons in their outer valence shell, so the energetically preferred state of achieving a filled electron shell is to lose two electrons to form doubly charged cations, M2+
eBook - PDFFoundations of Chemistry
An Introductory Course for Science Students
- Philippa B. Cranwell, Elizabeth M. Page(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
The term alkaline comes from the pH of the compounds formed from the elements when allowed to react with air or water. The term earth is a historical name given to substances found as ores (for example, metal salts) that are insoluble in water and stable on heating. Many compounds of Group 2 elements fit this description. The periodic table shows the members of Group 2 to consist of beryllium, magnesium, calcium, strontium, barium, and radium. Calcium and magnesium are the sixth and eighth most abundant elements, respectively, in the earth ’ s crust. Box 11.2 As with Group 1, the heaviest member of this group, radium, is radi-oactive. Radium was discovered by Pierre and Marie Curie in 1898. They separated 1 mg of radium from 10,000 kg of pitchblende – an ore of uranium. Its name comes from the faint blue glow produced by the element as it decays. The property was used for many years in luminous paint for clock and watch hands and dials and also in treating some forms of cancer. However, its extreme radioactive nature means that it is rarely used today. Pierre Curie (1859 – 1906) and Marie Sklodowska Curie (1867 – 1934), c. 1903. Source: Magnus Manske, https://commons.wikimedia.org/wiki/File:Pierre_Curie_ (1859-1906)_and_Marie_Sklodowska_Curie_(1867-1934),_c._1903_ (4405627519).jpg, licensed under CC0 1.0 Universal (CC0 1.0). 358 The periodic table 11.3.1 Physical properties of Group 2 elements The elements in Group 2 are all metallic in nature with typical properties of metals, although the first member of the group, beryllium, shows some differ-ences. The metals are all silvery grey when pure, although magnesium and beryl-lium react slowly with air to become coated with a thin layer of the white metal oxide, MO, that prevents further reaction. Table 11.3 gives some physical prop-erties of the elements of Group 2. Atomic radii and ionisation energy The metallic radii of the elements increase on going down the group.
eBook - PDF- S C Siekierski, J Burgess(Authors)
- 2002(Publication Date)
- Woodhead Publishing(Publisher)
Because of their large radii, organometallic compounds of Ca, Sr and Ba are highly ionic and reactive. As is the case with alkali metal hydrides the Group 2 hydrides MH 2 contain the Ir anion, except for BeH 2 and MgH 2 where there is a high contribution from covalency to the bonding. The Group 2 elements do not show the +I oxidation state. This is 78 Group 2. The allm 200 100 Ba= Ra-, Sr--.. ' ', Ca-, ','= ',, °'-..-..:~ ', ,, ·----i ,, 11 ,1 I Mg-__ 1~, ---,,, 1 , ,1 Ra2+ Be-..., ' ','-', '-Ba 2 + ', '-sr2+ '-----, I '-Ca 2 + I '-Mg2+ ''-Be 2 + -Ba ..... :..~-Ra ,,.-;/,...-Sr // / _,, / _,, ,...' -i:-Ca / / ---// / / _,-/ / ___, / / ,r--Be / -3 -4 -11' ens /eV -5 -6 -7 -8 -9 = R ns -1 1 6ns f; O'--~~~~~~~~-C_N~6~~~~~~~~~~~-10 r rret Fig. 8. l Radii, energy of m orbitals and first ionization potentials of Group 2 elements. Changes of chemical properties going down the Group result from changes in R ( = (rns> ), ri, rmel' &ns and 1 1 +1 2 . These are, as a mle, irregular (Fig. 8.1). In particular we observe: -Large changes in 1 1 , &ns' rmet and ri between beryllium and magnesium. The reason is the same as that found in the case of lithium and
eBook - PDFInorganic Chemistry
Butterworths Intermediate Chemistry
- C. Chambers, A. K. Holliday(Authors)
- 2016(Publication Date)
- Butterworth-Heinemann(Publisher)
110 6.1 The elements 6.1.1 General characteristics These elements form two groups, often called the alkali (Group I) and alkaline earth (Group II) metals. Some of the physical properties usually associated with metals — hardness, high m.p. and b.p. — are noticeably lacking in these metals, but they all have a metallic appearance and are good electrical conductors. Table 6.1 gives some of the physical properties. From Table 6.1, it is easy to see that Group II metals are more dense, are harder and have higher m.p. and b.p. than the corresponding Group I metals. In Chapter 2, a discussion of the theory of metallic bonding indicated that the strength of such bonding generally depends on the ratio (number of electrons available for bonding)/(atomic radius). The greater this ratio is, the stronger are the bonds between the metal atoms. In the pre-transition metals, this ratio is small and at a minimum in Group I with only one bonding electron. Metallic bond strength is greater in Group II but there are still only two bonding electrons available, hence the metals are still relatively soft and have low melting and boiling points. Hardness, m.p. and b.p. all decrease steadily down Group I, the metallic bond strength decreasing with increasing atomic radius. These changes are not so well marked in Group II but note that beryllium and, to a lesser extent, magnesium are hard metals, as a result of their small atomic size; this property, when coupled with their low density, makes them of some technological importance (p. 113). A full discussion of the changes in ionization energy with group and period position has been given in Chapter 2. These data are given again in Table 6.2. 6.1.2 Formation of ions We note first that the elements are all electropositive, having relatively low ionization energies, and are, in consequence, very reactive.
eBook - PDFChemistry
An Industry-Based Introduction with CD-ROM
- John Kenkel, Paul B. Kelter, David S. Hage(Authors)
- 2000(Publication Date)
- CRC Press(Publisher)
Li Na K Rb Cs Fr The Periodic Table 85 of other alkali metals. The only naturally occurring isotope of cesium, cesium-133, is used as the world’s official measure of time. Francium is radioactive (all isotopes) and unstable. 4.4.2 Alkaline Earth Metals Beryllium, magnesium, calcium, strontium, barium, and radium are the alkaline earth metals. They are grayish white in color and vary in hardness from being able to scratch glass (beryllium) to being soft as lead (barium). They are chemically reactive, but less so than the alkali metals. They are, for the most part, not stable in air, reacting with oxygen to form the metal oxide with the formula MO. In fact, magnesium, strontium, and barium will actually burn in the presence of air, magnesium emitting an extremely bright light in the process. They also react with water to form hydrogen gas (H 2 ) and the metal hydroxide [M(OH) 2 ], but not in the violent manner by which the alkali metals are known to react. Like the alkali metals, however, their reactivity is such that they are never found in the free elemental state in nature. The precious gems of emerald and aquamarine are forms of the mineral beryl, a com-pound of beryllium, silicon, and oxygen. Compounds of magnesium are found in two consumer products. Magnesium hydroxide [Mg(OH) 2 ] is the active ingredient in milk of magnesia, and magnesium sulfate (MgSO 4 ) is the active ingredient in Epsom salt. Calcium is found in human teeth and bones, hard water, and limestone, which is an ingredient in cement. Strontium compounds are used in fireworks, emitting a red-colored light. A com-pound of barium, BaSO 4 , is the white solid in the suspension we swallow so that x-rays can be taken of our intestinal tract. Radium has 25 known isotopes, the most common of which is radium-226, the form of radium discovered by Marie Curie (see CPW Box 3.2). 4.4.3 Halogens The halogens, fluorine, chlorine, bromine, iodine, and astatine, are a group of highly reactive nonmetals.
- Maria Csuros, Csaba Csuros(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
13 13 2 Discussion of Metallic Elements 2.1 REPRESENTATIVE ELEMENTS As discussed in Chapter 1, in the traditional numbering system of the periodic table, the A group el-ements are called main groups or representative elements . Only a few metallic elements occur in na-ture as free metals. All seven metallic elements known to the ancients (gold, silver, copper, iron, lead, mercury, and tin) have been found in the metallic state. Metals are too reactive chemically to be found in quantity as metallic elements. Except for gold, the metallic elements are obtained principally from their naturally occurring solid compounds or ores. A major source of metals and their compounds is the Earth’s crust. Minerals are naturally occurring inorganic substances or solid solutions with a definite crys-talline structure. Thus, a mineral might be a definite chemical substance, or it might be a homoge-neous solid mixture. Rock is a naturally occurring solid material composed of one or more minerals. An ore is a rock or mineral from which a metal or nonmetal can be economically produced. Representative metal groups are listed below. Group IA (1): lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr) Group IIA (2): beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra) Group IIIA (3): aluminum (Al), gallium (Ga), indium (In), thallium (Tl) Group IVA (4): tin (Sn), lead (Pb) Group VA (5): bismuth (Bi) 2.1.1 G ROUP IA (1): A LKALI M ETALS Alkali metals are soft and the most reactive of all metals; they are never found as free elements in na-ture, as they always occur in compounds. The pH of their aqueous solution is alkaline. All alkali met-als are typically metallic in character, with a bright luster and high thermal and electrical conductiv-ity. They have low densities because they have large atoms; large atoms lead to small ratios of mass per volume (density = mass/volume).
eBook - PDFThe History and Use of Our Earth's Chemical Elements
A Reference Guide
- Robert E. Krebs(Author)
- 2006(Publication Date)
- Greenwood(Publisher)
For example, they all are called alkaline earths because, when first discovered, they exhibited both characteristics of alkaline (basic) substances and characteristics of the earth from which they came. Ancient humans did not know they were metals because their metallic forms do not exist in nature. Barium is a silvery metal that is somewhat malleable and machineable (can be worked on a lathe, stretched and pounded). Its melting point is 725°C, its boiling point is about 1640°C, and its density is 3.51 g/cm 3 . (The accurate figures for its properties are difficult to determine because of barium’s extreme activity—the pure metal will ignite when exposed to air, water, ammonia, oxygen, and the halogens.) Characteristics When barium burns in air, it produces barium oxide (2Ba + O 2 → 2BaO). When metallic barium burns in water, it forms barium hydroxide [Ba + 2H 2 O → Ba(OH) 2 + H 2 ↑]. Several barium compounds burn with a bright green flame, which make them useful for fireworks. Barium is more reactive with water than are calcium and strontium. This is a result of the valence electrons’ being further from the positive nucleus. Therefore, barium is more electro- negative than the alkali earth metals with smaller nuclei. In powdered form, it will burst into a bright green flame at room temperature. Abundance and Source Barium is the 17th most abundant element in the Earth’s crust, making up about 0.05% of the crust. It is found in the minerals witherite, which is barium carbonate (BaCO 3 ), and barite, known as barium sulfate (BaSO 4 ). Pure barium metal does not exist on Earth—only as compounds or in minerals and ores. Barium ores are found in Missouri, Arkansas, Georgia, Kentucky, Nevada, California, Canada, and Mexico. ELECTRON CONFIGURATION Energy Levels/Shells/Electrons Orbitals/Electrons 1-K = 2 s2 2-L = 8 s2, p6 3-M = 18 s2, p6, d10 4-N = 18 s2, p6, d10 5-O = 8 s2, p6 6-P = 2 s2
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
