Different Types Of Atomic Bonds And Crystal Structures Biology Essay

The atomic construction of any component is made up of a karyon with positively charged, impersonal atoms and negatively charged negatrons that surround the karyon. Chemical bonds involve negatrons sharing or reassigning between atoms.

There are some typical bonds, such as ionic bonds, covalent bonds, metallic bonds and H bonds. The solid constructions depend on the manner the atoms or molecules arrange themselves. There exists 14 different types of crystal unit cell structures or lattice in nature ( NDT-Education, nd.a ) . The unit cell is the smallest constituent. The whole crystal can be generated by reiterating the unit cell ( Lister and Renshaw, 2000 ) . This essay will discourse the different types of chemical bonds and crystal constructions.

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Ionic bonding occurs when negatrons are transferred from atoms ( normally metals ) to other atoms ( normally non-metal ) . As a consequence, each new charged atom can accomplish a full outer shell ( Octet Rule ) . Figure 1 below shows the Lewis Structure ( point and cross ) of Na chloride molecule.

Figure1. The Lewis Structure of NaCl ( NDT- Education, nd.a )

Since each negatron has a negative charge, the Na atom that loses negatrons will ensue in being positively charged ( cation ) . Alternately, the chloride atom that additions excess negatrons becomes a negatively charged ion ( anion ) .

Sodium chloride is considered a typical ionic solid. It has a elephantine Attic construction since there possibly one million millions of Na ions and chloride ions held together by this electrostatic attractive force ( lane, 2010 ) . The little portion of Na chloride construction can be shown in Figure 2 ( a ) . The cation ( Na ) in the Centre is surrounded by six chloride ions. And each chloride is besides surrounded by six Na ions. With this ground, Na chloride is described as being 6:6 coordination ( Lister and Renshaw, 2000 ) .


The stronger attractive force between cations and anions can take to the more energy released. The more energy released causes the construction to go more stable ( Chemguide, 2008 ) . Before the anions touch each other, the maximal figure of chloride ions around the cardinal Na ion is six, which is the most stable. When the anions start touching, the crystal will go less stable due to the repulsive forces between negative atoms ( Chemguide, 2008 ) . Owing to a big size of the cesium ions, the cesium chloride construction is 8:8 coordination ( Lister and Renshaw, 2000 ) .

Compounds with ionic bonds have high thaw temperatures ( Lister and Renshaw, 2000 ) . They will non carry on electricity when solid. However, when melted or dissolved in H2O, they are music directors of electricity, because the charged ions are free to travel and can transport a current ( Lister and Renshaw, 2000 ) .

Covalent Molecules

A covalent bond is normally formed by non-metal atoms traveling near together. They can portion braces of negatrons. Each atom becomes stable by obtaining a full outer shell ( eight ) . Molecular covalent compounds may be solids, liquids or gases.

Although the covalent bonds between atoms ( interatomic ) are strong, the bonds between molecules ( intermolecular ) are weak, so the substances with covalent bonds have low thaw and boiling temperatures ( Lister and Renshaw, 2000 ) . With no charged atoms, these compounds are non good at carry oning electricity in any province ( Lister and Renshaw, 2000 ) . However, there are some differences in elephantine covalent molecules. The covalent bonds within elephantine molecules become a web widening throughout the compound.

Elephantine covalent constructions are variable depending on the agreement of atoms. Allotropes are different signifiers of the same component ( Lane, 2009 ) . Although diamond and black lead is allotropes of C, they have different constructions and belongingss.

Diamond has a three- dimensional ( 3D ) construction ( Lane, 2009 ) . As Figure 3 shows, each C forms four individual covalent bonds with next C atoms.

The strong carbon-carbon covalent bonds in 3D construction cause diamond to go the hardest natural substances and have a really high thaw point ( around 4000K ) ( Lister and Renshaw, 2000 ) . With such hardness, diamonds can be used industrially to tip drills ( Lister and Renshaw, 2000 ) .

Compared with diamond, black lead has a two- dimensional construction ( Figure 4 ) . The C atoms use three of its negatrons to organize individual bonds. The 4th negatrons become delocalized and a negative system over the whole bed ( Lister and Renshaw, 2000 ) .

Since the delocalized negatrons freely move throughout the sheets, black lead besides conducts electricity ( Lister and Renshaw, 2000 ) . In this construction, the distance ( 2.5d ) between beds is about 2.5 times the distance ( vitamin D ) between two atoms in the same bed ( Chemguide, 2000a ) . The extra bonding caused by the delocalized system make the covalent bonds within black lead strong, while the bonds between the beds are weak ( Chemguide, 2000a ) . As a consequence, the beds can skid over each other easy. When used as in pencils, the beds can be rubbed off to lodge to the paper ( Chemguide, 2000a ) .

Metallic bonds are formed in metals or metals of metals. The negatrons from the outer shell freely move around the atoms and organize a pool called a ‘sea of negatrons ‘ ( Lister and Renshaw, 2000 ) . Metallic elements are able to carry on heat and electricity easy since there are considerable nomadic negatrons in the ‘sea ‘ ( Lane, 2009 ) . The sea structures besides make metals have high thaw point. Ductility and plasticity are other belongingss of metals ( Lister and Renshaw, 2000 ) .

Some metals have unit cell constructions referred to hexagonal close wadding ( HCP ) ( Figure 5 ) . As shown in Figure 5 ( B ) , the HCP construction has three beds of atoms. There are 12 atoms in the corners of the top and bottom beds. Each atom contribute 1/6 atom to the unit cell ( 12 -1/6=2 ) . Two atoms in the centre of the top and bottom beds each contributes 1/2 atom ( 2 -1/2=1 ) . In the in-between bed, three atoms each contributes 1 atom ( 3-1=3 ) . Therefore, there are six ( 2+1+3 ) atoms in each unit cell.

As Figure 6 shows, the HCP has a manner of set uping beds called ABA, in which the 3rd bed is placed straight above the first 1 ( Lister and Renshaw, 2000 ) . It has a coordination figure of 12 since there are 12 next atoms around the atom in the centre. The volume of atoms in a unit cell busying the entire volume of the cell is called the wadding factor ( NDT -Education, nd.c ) . It can be calculated by ( NatomsVatom ) /Vunit cell, where Natoms is the entire figure of atoms in each unit cell, Vatom is the volume of one atom, and Vunit cell is the volume of the unit cell ( NDT -Education, nd.c ) . The HCP has a packing factor of 0.74 ( Lister and Renshaw, 2000 ) .

Another common wadding is body- centered cubic ( BCC ) . As Figure 7 shows, there are 8 atoms in the corners of the top and bottom beds. Each atom contribute 1/8 atom to the unit cell ( 8 -1/8=1 ) . One atom in the centre contributes 1 atom. Therefore, each BCC unit cell consists of two atoms ( Lane, 2009 ) . The coordination figure is 8 and the wadding factor is 0.68 ( Lister and Renshaw, 2000 ) .

Like H2O molecules, simple molecules are another type of solid construction. The H2O molecule has covalent bonds between an O atom and two H atoms. Water molecules can be arranged in a diamond construction ( Figure 8 ) .

Electronegativity is a comparatively step of a specified atom ‘s ability to pull negatrons ( Lewis, 2000 ) . Since H atoms are bonded to electronegative atoms ( O ) and solitary brace of negatrons from O, there exists H bonds to keep one H2O molecule to other molecules ( Lister and Renshaw, 2000 ) . Due to the H bonds, the molecules are less closely packed than in liquid province. Therefore, ice is less heavy than H2O. This prevents H2O stop deading from deep to come up. It allows oceans to stay liquid and fish to last ( Lane, 2009 ).

In decision, different chemical bonds have different characteristics. Compared with covalent bonds, ionic bonds have transferred negatrons instead than shared negatrons. Metallic bonds form ‘sea of negatrons ‘ . Different structures do different belongingss. For illustration, the elephantine construction makes diamond and black lead have high thaw points. The freely traveling or delocalized negatrons cause ionic molecules ( liquid province and aqueous solution ) , metals to carry on electricity. Metallic elements have different unit constructions, such as simple cubic, HCP, BCC. Some stuffs seem to hold assorted character. For case, with covalent, ionic and metallic negatron sea, black lead can carry on electricity good.