The melting point of aluminum is 660° Celsius.
Aluminum is an active metal, and a dense oxide film about 50 angstroms thick is immediately formed on the surface of aluminum in dry air, so that aluminum will not be further oxidized and can be resistant to water; but aluminum powder is easily combustible when mixed with air; molten aluminum can be mixed with Water reacts violently; aluminum is amphoteric, easily soluble in strong bases, and also soluble in dilute acids. The characteristics of aluminum are as follows:
- Aluminum is a silver-white light metal, relatively soft, with a density of 2.7 grams per cubic centimeter, a melting point of 660.4 degrees, and a boiling point of 2467 degrees. Aluminum and aluminum alloys have many excellent physical properties and have been widely used. The surface of aluminum generally has an aluminum oxide film. In normal life, when the aluminum that reaches the melting point is above 660 degrees, metal aluminum droplets will be formed. Therefore, generally, metal aluminum below 660 degrees is solid, and metal aluminum above 660 degrees is liquid.
- Aluminum has good reflective performance to light, and reflects ultraviolet rays stronger than silver. The purer the aluminum, the better its reflective ability. The method of vacuum aluminum coating is often used to make high-quality mirrors. The combination of vacuum aluminized film and polysilicon film becomes a cheap and lightweight solar cell material. Aluminum powder can maintain a silvery white luster and is often used to make coatings, commonly known as silver powder.
- The conductivity of pure aluminum is very good, second only to silver and copper. In the power industry, it can replace part of copper as wires and cables. Aluminum is a good conductor of heat, and aluminum can be used in industry to manufacture various heat exchangers.
According to the reducibility of aluminum, it can be inferred that aluminum can react with water, but the experiment found that aluminum has almost no reaction with boiling water. The dense oxide film prevents the reaction from proceeding further.
How To Explain The Melting Point Of Aluminum Is Similar To The Melting Point Of Magnesium?
The density of metallic magnesium is 1.74g/cm3 at 20°C, and the density of liquid metallic magnesium is 1.58q/cm3; under standard atmospheric pressure, the melting point of metallic magnesium is (650+1)°C, and the boiling point is 1,090°C. Magnesium metal starts to burn at 632-635%C when heated in air. And the density of metal aluminum at 200 is 2.70g/cm3, and the density of liquid metal aluminum is 2.38g/cm3; under standard atmospheric pressure, the melting point of metal aluminum is 660.4 ° C, and the boiling point is 2,519 ° C. Next, we will discuss why the aluminum melting points of the two are very close? Two trends of melting points, – IV>II>II>I group; and period 2>3. – In general, the melting point of an element depends on the “bonding nature” and “structure” of the element. It is not difficult to understand that if there is a strong attraction between metal atoms, more energy is required to overcome this attraction, such as tungsten (5,828 K), which is exceptionally high.
So What Is Bonding Essence? What Is Structure?
The force existing inside the metal is called “metal bond I (electrostatic interaction between metal cations and free electrons). The strength of the metal bond determines the melting point and hardness of the metal. Generally speaking, the stronger the metal bond, the higher the melting and boiling point of the metal. The greater the hardness. The strength of the metal bond is mainly determined by the metal’s “ionic radius J and the number of free electrons in the unit volume, J. The smaller the ionic radius, the greater the valence state and the stronger the metal bond. As for the giant metal structure, it refers to the Atoms are connected by “strong metal bonds”. When the third cycle is traversed from sodium to aluminum, the number of electrons participating in the formation of the metal piece increases, so the strength of the metal piece also increases. Therefore, more energy is required to overcome the metal bond and melt the metal, which explains the increase in melting point from sodium to cnc machining aluminum.
So What Does The Boiling Point Have To Do With It?
In metal crystals, metal atoms are bound together by the interaction between “free electrons” and “metal ion holes J”. When the metal is melted, the metal bonds are not destroyed, but the distance between atoms increases slightly; when the metal melts, the metal bonds are not destroyed. When the liquid metal is a gas, the metal bonds are completely broken and separated into individual atoms, so the boiling point of the metal tends to be much higher than the melting point. Figure 4 indicates the crystal structure of various metals at room temperature, among which magnesium is the hexagonal closest packing (FCP), while aluminum is face-centered cubic (FCO), and the filling rate of both is 74%, regardless of whether the metal element is densely packed. (Orbital weight and geometry): The tighter, the stronger the metal bond. Factors that affect the strength of metallic bonds include:
- The number of charges of the nucleus: the more the number of charges of the nucleus, the stronger the attraction, so the stronger the metal bond.
- The number of valence electrons: the more valence electrons, the stronger the metal bond and the higher the melting point of the metal.
- Atomic radius size: The larger the atomic radius, the weaker the nuclear valence electron attraction, the weaker the metal bond.
- Atomic packing (overlapping and geometry of orbitals): the tighter, the stronger the metal bond.
- The relationship between metal bond strength and periodic table 9:
- The metal bond of the same row of elements increases with the increase of the atomic number: because the number of valence electrons of the same row of elements increases with the increase of the atomic number, the atomic radius gradually decreases, and the number of electric nuclei of the nucleus gradually increases, so the stronger the metal bond is . Example: The heat of vaporization of the metal elements in the second, third, fourth, fifth and sixth columns increases with the increase of the atomic number. Example: Metal bond A/ >Mg > Na. (The stronger the metal bond, the higher the melting point and the higher the Mohr’s heat of evaporation)
- The strength of the metal bonds of the same group of elements is more irregular: because the number of valence electrons of the same group of elements is equal, but with the increase of the atomic number, its atomic radius is increasing, and the number of nuclear nuclei is also increasing. Two factors Conflict with each other, so the strength of metal bonds of the same group elements is less regular. For example: the metal bond of alkali metals gradually weakens with the increase of atomic number, Li>Na>K>Rb>Cs, but the alkali element 9 is irregular.
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