A general smashville247.netistrysmashville247.netTextmaporganized approximately the textbooksmashville247.netistry: Principles, Patterns, and also Applicationsby Bruce A. Averill


Learning Objectives

To define how to isolate the alkaline earth metals. Come be familiar with the reactions, compounds, and also complexes the the alkaline earth metals.

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Like the alkali metals, the alkaline planet metals room so reactive that they are never uncovered in elemental kind in nature. Because they form +2 ion that have very an adverse reduction potentials, huge amounts of power are required to isolate them from their ores. Four of the six team 2 elements—magnesium (Mg), calcium (Ca), strontium (Sr), and also barium (Ba)—were very first isolated in the beforehand 19th century by teacher Humphry Davy, using a technique similar come the one he provided to acquire the first alkali metals. In comparison to the alkali metals, however, compounds of the alkaline planet metals had been known as distinct for plenty of centuries. In fact, the surname alkali originates from the Arabic al-qili, definition “ashes,” i beg your pardon were well-known to neutralize acids. Middle ages alsmashville247.netists uncovered that a portion of the ashes would certainly melt on heating, and these substances were later determined as the carbonates that sodium and also potassium ((M_2CO_3)). The ashes the did not melt (but go dissolve in acid), originally dubbed alkaline earths, were subsequently determined as the alkaline planet oxides (MO). In 1808, Davy was able to acquire pure samples the Mg, Ca, Sr, and also Ba by electrolysis of your chlorides or oxides.

Beryllium (Be), the lightest alkaline earth metal, was an initial obtained in 1828 through Friedrich Wöhler in Germany and also simultaneously by Antoine Bussy in France. The technique used through both men was palliation of the chloride through the potent “new” reductant, potassium:

Radium was found in 1898 through Pierre and Marie Curie, who processed tons of residue from uranium mines come obtain about 120 mg of nearly pure (RaCl_2). Marie Curie was awarded the Nobel prize in smashville247.netistry in 1911 for its discovery. Since of its low abundance and also high radiation however, radium has couple of uses.

Preparation the the Alkaline earth Metals

The alkaline earth metals are produced for commercial use by electrolytic palliation of their molten chlorides, as shown in this equation for calcium:

The team 2 steel chlorides are derived from a range of sources. For example, (BeCl_2) is developed by reacting (HCl) through beryllia ((BeO)), which is acquired from the semiprecious rock beryl ().

A decision of beryl. Beryl is a gemstone and vital source of beryllium.

smashville247.netical reductants can also be supplied to achieve the team 2 elements. Because that example, magnesium is developed on a large scale by heating a type of limestone called dolomite (CaCO3·MgCO3) v an inexpensive iron/silicon alloy at 1150°C. Originally (CO_2) is released, leaving behind a mixture of (CaO) and also MgO; Mg2+ is then reduced:

<2CaO·MgO_(s) + Fe/Si_(s) ightarrow 2Mg(l) + Ca_2SiO_4;(s) + Fe(s) labelEq3>

An early source of magnesium to be an ore called magnesite ((MgCO_3)) native the district of northern Greece called Magnesia. Strontium was derived from strontianite ((SrCO_3)) discovered in a lead mine in the town of Strontian in Scotland. The alkaline earth metals space somewhat less complicated to isolate from their ores, as contrasted to the alkali metals, since their carbonate and some sulfate and also hydroxide salts room insoluble.

A crystal of strontianite. Both strontianite, one of the most vital strontium ores, and also strontium are named after the city of Strontian, Scotland, the ar of one of the first mines because that strontium ores.

General properties of the Alkaline earth Metals

Several crucial properties the the alkaline earth metals are summarized in Table (PageIndex1). Although plenty of of this properties are similar to those of the alkali steels (Table (PageIndex1)), certain an essential differences space attributable come the distinctions in the valence electron configurations of the two teams (ns2 for the alkaline earth metals matches ns1 because that the alkali metals).

Table (PageIndex1): Selected nature of the group 2 aspects BerylliumMagnesiumCalciumStrontiumBariumRadium *The worths cited are for six-coordinate ions except for Be2+, for which the value for the four-coordinate ion is given.
atomic symbol Be Mg Ca Sr Ba Ra
atomic number 4 12 20 38 56 88
atomic mass 9.01 24.31 40.08 87.62 137.33 226
valence electron configuration 2s2 3s2 4s2 5s2 6s2 7s2
melting point/boiling suggest (°C) 1287/2471 650/1090 842/1484 777/1382 727/1897 700/—
density (g/cm3) at 25°C 1.85 1.74 1.54 2.64 3.62 ~5
atomic radius (pm) 112 145 194 219 253
first ionization energy (kJ/mol) 900 738 590 549 503
most typical oxidation state +2 +2 +2 +2 +2 +2
ionic radius (pm)* 45 72 100 118 135
electron affinity (kJ/mol) ≥ 0 ≥ 0 −2 −5 −14
electronegativity 1.6 1.3 1.0 1.0 0.9 0.9
standard electrode potential (E°, V) −1.85 −2.37 −2.87 −2.90 −2.91 −2.8
product that reaction with O2 BeO MgO CaO SrO BaO2
type of oxide amphoteric weakly basic basic basic basic
product the reaction through N2 none Mg3N2 Ca3N2 Sr3N2 Ba3N2
product of reaction through X2 BeX2 MgX2 CaX2 SrX2 BaX2
product of reaction through H2 none MgH2 CaH2 SrH2 BaH2

As v the alkali metals, the atomic and also ionic radii of the alkaline planet metals increase smoothly from it is in to Ba, and the ionization energies decrease. Together we would certainly expect, the very first ionization power of one alkaline earth metal, through an ns2 valence electron configuration, is constantly significantly higher than the of the alkali metal instantly preceding it. The team 2 elements do exhibit some anomalies, however. For example, the density of Ca is much less than that of Be and also Mg, the 2 lightest members that the group, and Mg has the lowest melting and also boiling points. In comparison to the alkali metals, the most heavy alkaline earth metal (Ba) is the the strongest reductant, and also the lightest (Be) is the weakest. The typical electrode potentials the Ca and Sr space not very different from that of Ba, indicating that the opposing patterns in ionization energies and hydration energies are of about equal importance.

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One significant difference between the group 1 and group 2 facets is your electron affinities. V their half-filled ns orbitals, the alkali metals have actually a far-ranging affinity for secondary electron. In contrast, the alkaline earth metals typically have small or no propensity to accept an additional electron due to the fact that their ns valence orbitals are already full; an added electron would need to occupy one of the vacant np orbitals, which room much greater in energy.