Structure of metals

Structure and bonding in metals:

Metals consist of giant structures of atoms arranged in a regular pattern. The electrons from the outer shell of the metal atoms are delocalised and are free to move through the whole structure. This sharing of Delocalised electrons results in a strong metallic bond.

Metallic bond: 

Metallic bonds formed when the charge is spread over a large distance as compared to the size of a single item in a solids. Mostly in the periodic table, left elements form metallic bonds, for example zinc and copper. Because metals are solid, their atoms are tightly packed in a regular arrangement. They are so close to each other so valence electrons can be moved away from their atoms. A sea of free, Delocalised electron is formed surrounding a lattice of positively charged metal ions.These ions are held by strong attractive forces to mobile electrons,in this way, metallic bonds are formed.

Structure of metals:

The three most common crystalline structures in metals are face centered cubic, body centered cubic, and hexagonal close packed.

Face-centered cubic:

One of the most common crystalline structures is face centered cubic (FCC). The FCC crystalline structure gets its name from its cube shape and the location of atoms within that cube. There are 8 atoms that are distributed among the 8 corners of the crystalline structure. Each of those 8 atoms are part of another adjacent cubic structure as well. In addition to the atoms located on the corners of the FCC structure, there are also 6 atoms located on the centre of each cube face, hence the name face centered cubic.

There are many different types of metal with the FCC crystalline structure. The two examples in the introduction, aluminium and lead, are two metals that have the FCC structure at room temperature, but when heated to a certain temperature, the typical ferrite body-centered cubic found in an iron begins to transform to austenite, which does have an FCC crystalline structure.

Body centered-cubic: 

The body centered-cubic(BCC) crystalline structure is another abundant type of atomic structure found in metals. Like the FCC crystalline structure the BCC crystalline structure gets its name from its shape. The BCC crystalline structure is in the form of a cube with 8 atoms distributed among the eight corners similar to the FCC crystalline structure. What is the difference about the BCC crystalline structure is that rather than having an atom at each of the 6 faces, it has only one atom that is inside the cube. This atom is centered in the body cube, which is the reason for the name body centered-cubic.

Many metals are composed of the BCC crystalline structure. As previously mentioned iron in its ferrite form is a member of the BCC family of metals. Also falling under the BCC crystal in the structure umbrella at room temperature New BM chromium and vanadium. Potassium, lithium, sodium and other alkaline metals are also typically constructed by the BCC crystalline structure.

Hexagonal closed-packed:

Hexagonal closed-packed (HCP) is a crystalline structure that is somewhat more complex than the FCC and BCC crystalline structures. If one hexagonal close-packed structure adjacent to it,it would be composed of 17 atoms. There are 6 atoms  spread evenly among each vertex of a hexagon. An additional 6 atoms are distributed equally across the vertices of another hexagon. Additionally there is an atom in the centre of each of these hexagons. Both groups of atoms in the hexagons are aligned with one another. Sandwiched or packed, in between these two hexagons is a group of three atoms that are not in line with the atoms in either of the hexagons.The atoms in the hexagons are shared with adjacent HCP structures

The HCP crystalline structure is found in several different metals.Titanium and cadmium are two of the most commonly used metals that comprise the HCP crystalline structure at room temperature. Cobalt, zinc and zirconium are a few other well-known examples.

Source: internet