TLDR;
The alkaline earth metals, found in Group 2 of the periodic table, are characterised by having two valence electrons, making them reactive reducing agents. The video explores their properties, reactivity, and various applications, from construction and lightweight materials to essential biological functions and uses in fireworks and medicine. The reactivity of these metals increases as you move down the group from beryllium to radium due to the weakening hold on their valence electrons.
- Alkaline earth metals are reactive due to their two valence electrons.
- Their applications range from aerospace to medicine.
- Reactivity increases down the group from beryllium to radium.
Introduction to Alkaline Earth Metals [0:02]
Alkaline earth metals are generally softer than most other metals and react readily with water, especially when heated. Each has two valence electrons in its outermost shell, making them powerful reducing agents that easily give up electrons. Beryllium can absorb large amounts of heat, making it useful in spacecraft and aircraft construction. Magnesium, a light metal, is combined with others to make lightweight and strong products like racing bicycles, airplanes, and missiles. Calcium is essential for living organisms, forming the basis for shells, teeth, and bones. Strontium is used in colourful flares, fireworks, and phosphorescent paints, while a radioactive version is a deadly byproduct of nuclear fallout. Barium, a heavy silver metal, is used in spark plugs, vacuum tubes, and fluorescent lamps. Radium, intensely radioactive, was once used to destroy cancer cells.
Physical Properties [1:26]
In their pure forms, alkaline earth metals are shiny, silvery-grey metals with relatively high melting and boiling points, and they are good conductors of heat and electricity. Freshly cut, they have a grey-white lustre but tarnish quickly in air, with heavier members tarnishing especially quickly. Beryllium, the lightest, is hard enough to scratch glass, while barium, the heaviest, is only slightly harder than lead. These metals react readily with water, especially when heated, and combine easily with other elements, meaning they are never found in pure form in nature. Although harder, stronger, and denser than alkaline metals, they are nearly as chemically reactive.
Reactivity and the Periodic Table [2:28]
Alkaline earth metals are highly reactive because they are very electropositive, easily losing electrons to other elements. The periodic table lists elements by atomic number, representing the number of protons in the nucleus. In a neutral state, the nucleus is surrounded by an equal number of electrons. As the atomic number increases, so does the size and mass of the atoms. Horizontal lines are called periods, representing the number of electron shells. Vertical lines are called groups; elements in a group have the same number of valence electrons, dictating how they interact. Elements in the same group generally interact similarly.
Valence Electrons and Group 2 [4:01]
Elements with an atomic number greater than 83 are generally radioactive, including radium. All alkaline earth metals are in Group 2 because they each have two electrons in their outermost shell. Atoms need eight electrons in their valence shell to be stable, making alkaline earth metals unstable, nearly as unstable as alkaline metals with only one valence electron. As a result, alkaline earth metals easily lose their two electrons during chemical reactions. Moving from beryllium to radium, the hold on valence electrons weakens, making each alkaline earth metal more reactive than the one before it.
