The difference between them lies in the number of electrons outside the nucleus, which can be explained by the size of atomic radius. From sodium to magnesium to aluminum, the number of electrons outside the nucleus gradually increases, the attraction of outer electrons gradually increases, the atomic radius gradually decreases, and the ability to lose electrons gradually weakens, so the metallicity gradually weakens.

Metallurgy refers to the ability of atoms of metal elements to lose electrons in chemical reactions. The stronger the ability to lose electrons, the stronger the metallicity of the elements to which the particles belong; On the contrary, the weaker it is, the stronger its nonmetallic property is. The properties of metals often indicate the tendency of atoms of elements to lose electrons; The nonmetallic nature of elements refers to the ability of atoms of elements to acquire electrons.

Extended data:

The stronger the metallicity of an element, the more intense the reaction between its simple substance and water or acid, and the stronger the alkalinity of the corresponding alkali. For example, metal Na & gtMg & gtAl, Na reacts violently with water at room temperature, Mg reacts slowly with water, and Al reacts violently with water at room temperature.

Alkaline NaOH >: Mg(OH)2 > aluminum hydroxide. The stronger the nonmetal of an element, the more intense the reaction between its simple substance and H2, the stronger the stability of the obtained gaseous hydride, and the stronger the acidity of the hydrate corresponding to the highest valence oxide of the element.

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