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How do alkali metals differ from alkaline-earth metals?
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periodic table
Modern version of the periodic table of the elements. To learn an element's name, atomic number, electron configuration, atomic weight, and more, select one from the table.
Alkali metals and alkaline-earth metals differ primarily in their electronic structure, reactivity, and physical properties, as defined by their positions in the periodic table.
Electronic Structure and Ions
- Alkali Metals (Group 1): Each atom has a single valence electron in its outermost shell, leading them to form singly charged positive ions (cations) with a +1 oxidation state.2
- Alkaline-Earth Metals (Group 2): Each atom has two valence electrons in its outermost shell. Their chemistry is dominated by the formation of doubly charged M ions, and they exhibit an oxidation state of +2.1
Reactivity and Ionization
- Ionization Energy: Alkali metals have lower ionization energies than alkaline-earth metals, making them more electropositive and generally more reactive.2
- Electronegativity: Alkali metals are the least electronegative elements (ranging from 0.7 to 1.0), while alkaline-earth metals have slightly higher values (ranging from about 0.9 to 1.5).2
Physical Properties
- Melting and Boiling Points: Alkaline-earth metals generally have higher melting and boiling points than the corresponding alkali metals.1
- Density: Alkali metals are characterized by low densities; notably, lithium, sodium, and potassium are less dense than water.2