In order for atoms to gain a full shell of electrons, chemical bonding needs to occur by either gaining or losing electrons. Ionic, Covalent and Intermolecular bonds are the different types of atomic bonding (Hunt, A., 2000).
The process of ionic bonding occurs with both metals and non-metals (Ritchie, 1998, pp. 19 ‘ 25). The metal atoms consist of the first few columns of the periodic table, and these have spare electrons in their outer shell, meaning that they need to bond with a non-metal atom in order to gain electrons to have a full shell. The way in which this works is when electrons are transferred from the metal atom to the non-metal atom to form ions, and when this ionic bond happens, attractions are created between the positive and negative charge ions (Khan, 2013). As the electrons are traded and are accompanied ions of the opposite charge, and these opposite charges will attract each other, this forms the chemical bond (Khan, 2013).
(GCSE Bitesize: Dot-and-cross diagrams – compounds, 2011)
One example of this would be the bonding of magnesium and oxygen. Magnesium has an atomic number of 12 (12 protons in the nucleus) which is arranged in a 2,8,2 form, thus showing that magnesium has to lose 2 electrons in order to have a full outer shell(Harvey, 2012). In contrast, oxygen has the atomic number 8, which is arranged as 2,6. Therefore, oxygen needs to obtain 2 more electrons to complete the outer shell. So, as magnesium transfers 2 electrons, which oxygen gains, this gives magnesium a positive charge and oxygen a negative charge. This changes the formula of both, magnesium changes to Mg2+ and the oxide ion changes to O2 (Ritchie, 1998, pp. 19 ‘ 25).
In difference to ionic bonding, covalent bonding only occurs with non-metal atoms, where they need to share electrons in order to obtain a complete outer shell. The process of covalent bonding occurs in the nuclei. . The ways in which atoms are bonded are known as molecules, they are ‘held together by the attraction between the positive charges on their nuclei and the negative charge on the shared electrons’ (Hunt, A., 2000). There are two types of Covalent bond, the first is called the nonpolar covalent bond and the second is the polar covalent bond. When the electrons are shared equally and the bonded atoms are the same and have the same electronegativity are called non-polar covalent bonds. Polar covalent bonds differ as the atoms are different with a different electronegativity, and the electrons are pulled towards the more electronegative atoms. In addition, the molecules in polar covalent are lop-side which creates dipoles (Ritchie, 1998, pp. 19 ‘ 25).
Covalent bond only occurs within non-metal atoms. Non-metal atoms also try to attain a full outer shell structure by which they need to share electrons that belongs to both atoms in the bond. The shared electrons are attached at the nuclei, which then forms the covalent bonds. ‘The atoms are held together by the attraction between the positive charges on their nuclei and the negative charge on the shared electrons’ (Hunt, A., 2000). Atoms bonded this way are known as molecules. There are two types of Covalent bond, which are nonpolar covalent bond and polar covalent bond. Non-polar covalent bond is when the electron is shared equally and the bonded atoms are the same and have the same electronegativity. Polar covalent bond is when the bonded atoms are different and has a different electronegativity. The electrons in a polar covalent bond are pulled towards the more electronegative atoms, In polar covalent bond, molecules are lop-sided creating dipoles (Gilbert et al., 2011).
(GCSE Bitesize: Dot-and-cross diagrams – compounds, 2011)
The hydrogen atoms only has 1 electron on its outermost shell it needs to gain 1 more electron in order to get a complete outer shell which is the same for the other hydrogen molecule. However the oxygen has 6 electrons in total, but the 2 electrons occupy the first shell and the other 4 electrons make up the outer shell (Gilbert et al., 2011). The outer shell in oxygen atom needs to gain more electrons to enable it to reach a stable state by achieving its nearest noble gas configuration (2.6), In order for that to occur it needs to share 2 electrons with some other element’s. in H2O all of the elements require electrons to be stable, therefore they share it within each other. The oxygen shares its electrons with the hydrogen molecules making it 2 electrons on its outer shell, on the other hand the two hydrogen atoms share its only electron in order for the oxygen to get to a stable state making its outer shell 6 electrons. Hydrogen atoms can each form one covalent bond, while oxygen atoms can each form two covalent bonds. Two pairs of electrons are shared in a water molecule (H2O) (Clarkson, 2012).
There are three types of intermolecular interactions, which are Hydrogen bonding, vander Waals and Dipole-Dipole (Clarkson, 2012).
Hydrogen bonding is when Hydrogen is bonded to nitrogen, oxygen or fluorine. This happens due to the fact that oxygen, nitrogen and fluorine are very electronegative so they pull the bonding pair between them and hydrogen well away from the hydrogen, making it more positive (‘Intermolecular force’, 2015)
. Also nitrogen, oxygen and fluorine atoms have a lone pair of electrons which are attracted to the positive hydrogen atom. This force of attraction between an electron deficient hydrogen bonded to nitrogen, oxygen or fluorine and the lone pair of neighbouring nitrogen, oxygen or fluorine atom is called a hydrogen bond. The hydrogen bond is mainly defined as a strong electrostatic dipole-dipole interaction. However, it also has some qualities of covalent bonding and is much stronger than a van der Waals interaction (Gilbert et al., 2011).
(Gilbert et al., 2011)
The lone pairs on the electronegative oxygen are attracted to the partially-positive hydrogen atom on a different H2O molecule, this attraction causes the two molecules to stick to each other a little bit, which is a basis for hydrogen bonding. The contact of the electronegative oxygen with the hydrogen atoms from another molecule is very strong (All about Intermolecular Forces, 2014).
Van der Waals forces exist within all covalent molecules whether polar or non-polar. This is the weakest intermolecular interaction. Instantaneous dipole is when the electrons are unevenly spread so as to one side of the particle is slightly positive while the other is negative. This instantaneous dipole can encourage another dipole in the near particle. These two particle then attracts each other which creates an instantaneous dipole-induced attraction. These forces of attraction are the Van der Waals forces. Van der Waals is caused by electron fluctuation (Ritchie, 1998, pp. 19 ‘ 25).
Electrons in an atom are in constant motion, but at some point in time there are more electrons in one side creating negative and positive charges, which is known as an instantaneous dipole. Instantaneous dipole on one atom can induce an instantaneous dipole on another neighbouring atom and are oriented to cause an attractive force. The electrons within the atoms move around but move in sync with each other to preserve the attractive force (mtchemers, 2008).
Dipole-dipole forces are the forces found in between the positive end of a one polar molecule and the negative end of another polar molecule. These forces are much weaker than ionic or covalent bonds and only takes effect when the molecules involved are nearby each other (Ritchie, 1998, pp. 19 ‘ 25). This takes place when 2 polar molecules are near each other in space, when this happens the partially negative part of one of the polar molecules is attracted to the partially positive part of the second molecule (Ritchie, 1998, pp. 19 ‘ 25).
(Gilbert et al., 2011)
Dipole-dipole forces attract two polarised molecules. If the polarity of the molecules increases then the force of the dipole-dipole will increase (Gilbert et al., 2011).
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