What are red, blue and lead for?

Metal lead is a corrosion-resistant heavy nonferrous metal material. The original color of lead is bluish white, and its surface is quickly covered with a layer of dark gray oxide in the air. Lead has the advantages of low melting point, strong corrosion resistance, difficult penetration of X-ray and γ-ray, and good plasticity. It is often processed into plates and pipes, which are widely used in chemical industry, cables, batteries and radiation protection.

Red, blue and lead are only used for marks on books. Generally speaking, red marks indicate the key paragraphs marked by readers, while those blue marks are temporary notes and the like.

Extended data:

Lead is located in Ⅳ A family of the sixth period, with atomic radius of 146pm, Pb radius of 84pm, first ionization energy of 7 18.96kJ/mol, electronegativity of 1.8, and main oxidation numbers of +2 and +4. Silver-gray shiny heavy metal, which is easy to lose its luster by oxidation in the air, becomes gray, soft, weak and strong in ductility. The density is 1 1.34g/cm, the melting point is 327.5℃, and the boiling point is 1525℃. It has strong radiation resistance.

The recrystallization temperature of lead is lower than room temperature, and the pressure machinability is excellent without work hardening. Lead and lead alloys have low strength and hardness, especially low fatigue strength and creep strength, and are easily damaged by fatigue and creep, so attention should be paid to them when they are designed and used as components.

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