Table of Contents
Elements of Alkaline Earth Metals
Like alkaline metals, alkaline earth metals have basic properties, as opposed to acids. Alkaline earth metals are shiny, and most are white or silver in colour. Like their “cousins” in the alkali metal family, they shine in different colours when hot. Calcium glows orange, strontium glows bright red, and barium glows an apple green. Physically they are soft, though not as soft as alkali metals, many of which can be cut with a knife.
Also similar to the earth’s alkaline meta ls and alkaline metals is the fact that four of them — magnesium, calcium, strontium, and barium — were identified or separated during the first decade of the nineteenth century by the English chemist Sir Humphry Davy. 1778-1829. At the same time, Davy also separated sodium and potassium from the alkali iron family.
Alkaline earth metals are less effective than alkaline metals, but like alkali metals they are more effective than most compounds. And like their “cousins,” they react with water to produce hydrogen gas and metal hydroxide, though their reaction is much smaller than that of alkali metals. Magnesium in its purest form burns, and when exposed to air, it burns with intense white light, mixed with oxygen to produce magnesium oxide. Similarly, calcium, strontium, and barium react with oxygen to form oxides.
Due to their high regeneration rates, alkaline earth metals do not usually appear by themselves naturally; instead, they are often found in other compounds in a composite form, usually carbonate or sulphate. This, too, is somewhat similar to alkali metals. But while alkali metals usually form 1+ cations (well-charged atoms), alkaline earth metals form 2+ cations — that is, cation has a 2-point charge.
Melting & Boiling Points
Another way alkaline earth metals are separated from alkaline metals is about melting and boiling points — those temperatures, in turn, when solid metal becomes liquid, and liquid metal evaporates. In alkaline metals, temperatures of boiling and melting points are reduced by increasing the number of atoms. However, the pattern is less clear about alkaline earth metals.
The Abundance of Alkaline Earth Metals
In the alkaline earth iron, calcium is found in abundance. It is ranked fifth among Earth’s crust, accounting for 3.39% of the original weight. And it is the fifth most populous in the human body, at 1.4%. Magnesium, which makes up 1.93% of the earth’s crust, is the eighth most abundant resource on Earth. It is ranked seventh in the human body, accounting for 0.50% of body weight.
Barium is ranked seventeenth among Earth’s crust, although it accounts for only 0.04% of its initial weight. It or the other three alkaline metals do not appear in the body in insignificant amounts: indeed, barium and beryllium are toxic, and radium is so radioactive that exposure to it can be extremely harmful.
Within the Earth’s crust, strontium is present in the amount of 360 parts per million (ppm), in fact much larger than the number of objects. At sea, its presence is about 8 ppm. In contrast, the abundance of beryllium in the Earth’s crust is measured in parts per billion (ppb), and is estimated at 1,900 ppb. Very rare is radium, comprising just 0.6 trillion for each trillion of the Earth’s crust — a fact that made the French-Polish physicist and chemist Marie Curie (1867-1934) even more impressive.
Alkaline Earth Metals Reaction
All alkaline earth metals have two electrons in their valence shell, so they lose two electrons to form cations with a 2+ charge. Most of the chemicals have been identified only in the first five members of the group; the chemistry of radium is not well established due to its radioactivity.
Chemically, all alkaline metals react with halogens to form ionic alkaline Earth metal halides. All alkaline earth metals except beryllium also react in water to form solid alkaline hydroxides which must be treated with extreme caution. Heavy alkaline earth metals are stronger than light ones.
Alkaline metals have a very low second ionisation potential in their periodic table times. This is due to their low operating cost and the ability to detect the full outer shell configuration by losing only two electrons. The secondary ionisation potential of all alkaline metals is also low.
Beryllium is different. It does not react with water or steam, and its halides are strong. All compounds containing beryllium have a covalent bond. Even beryllium fluoride, a compound of ionic beryllium, has a low melting point and low electrical conductivity when dissolved.
Alkaline Earth Metals FAQs
Why are they called alkaline earth metals?
The name comes from the fact that the oxides of these metals produce basic solvents when dissolved in water, and they remain stable at temperatures found in ancient alchemists. Like the elements of Group 1, alkaline earth metals are highly efficient so that they can be found in nature in their original form.
What is the difference between alkali and alkaline earth metals?
The main difference between alkali and alkaline earth metals is that alkali metals have one valence electron in the outer layer while alkaline earth metals have two valence electrons in the outer layer.
What is the reaction of alkaline earth metals?
All alkaline earth metals respond with halogen to produce a corresponding halide, with oxygen to form oxide except barium, which forms peroxide, and heavy chalcogens to form chalcogenides or polyhalogenated ions.