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Both Potassium and Sodium are highly reactive group 1, meaning they both contain 1 electron in their outer shell. 

Na has an atomic number of 11. Therefore based on the 2-8-8 rule of electrons Na holds its electrons in 3 shells. With the valence electron being in the third shell. 

K has an atomic number of 19, meaning it holds its valance electron within the 4th shell. 

The nucleus of every atom is positively charged due to the presence of Protons. These protons form electrostatic forces of attraction with oppositly charged electrons surrounding the nucleus. The electrostatic forces of attraction are greatest between the nucleus and atoms in shells which are closer to the nucleus. 

In the case of Na these electrostatic forces of attraction are spread across 3 shells compared to 4 shell in K. This means the electrostatic force of attraction between the valance electron of K and it nucleus is weaker than that of Na. 

This means less energy is required to break the electrostatic force of attraction with the valance electron in K compared to Na, meaning it is more willing to oxidise and lose an electron. 

Even though K has more protons than than Na, the force of attraction between the valance shell electron and the nucleus is weaker in K than in Na because the of the presence of more shells (the shielding effect). 

Chemistry

Why is potassium more reactive than sodium?

Bond energy is the amount of energy required to break 1 mol of bonds, in order to separate atoms into their gaseous state. 

Bond energy depends on the radius of the atoms within the molecules. As the radius of the atoms increase the strength of the bond decreases. Bond energy also depends on the type of bonds present - for example the presence of sigma, pi and delta bonds. Bond energy can also be impacted by the presence of lone pairs of electrons in the bonded atoms, as this increases the Coulumbs forces of repulsion, since same charges repel. 
 

Intermolecular energy is the energy between molecules. This energy is held in intermolecular bonds such as Hydrogen bond. Which are the forces of attraction of Hydrogen (with a positive dipole) and a lone pair of electrons on atoms such as Oxygen, Nitrogen and Fluorine. Other types of intermolecular forces include Permanent and Spontaneous Dipole Dipole interactions which are due to the electronegativity of bonded atoms, the random movement of electrons and the formation of Dipoles which leads to the formation of Coulumbs forces of attraction and repulsion. 

Another type of intermolecular forces of attraction is Ion Dipole interactions which occurs between an Ion and an atom with an opposite Dipole moment. 


Difference between bond energy and intermolecular energy

Both Na and K are Group 1 metals, meaning they possess 1 electron in their valance shell of electrons. 
K is further down in group 1 because it has more electron shells. 

K also has more protons than Na, this would lead one to assume that the nuclear force of attraction between the positive nucleus and the valance shell of electrons would be stronger (since opposite charges attract), however, due to the greater number of shells between the nucleus and the outer shell, more shielding of the nuclear attraction occurs. This means less energy is required to break the forces of attraction between the nucleus and outer shell electron in Potassium compared to Sodium. Thus increasing the reactivity. 

Which is more reactive between sodium and potassium?

Hi Bethany, 

Please contact me and we can discuss in more detail exactly which topics you would like help with as well as what your goals are in Biology. 



Biology

Biology exam later need a learn a little more on biology

Hi Macy, 

I would recommend that you do Biology and Chemistry and then a third subject of your choice. Although, 4 A-Levels is not a requirement for most medical and veterinary schools it might be worth considering if you think you would be able to manage to work and still achieve top grades. 

My next piece of advice would be to do as much work experience as you can such as a boarding kennel for dogs or a veterinary practice. This will make you stand out amongst other candidates. 

Gurjeet Cheema

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