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Explain what is meant by the following terms: i) Oxidising agent: ii) Displacement reaction: iii) Electronegativity

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Explain what is meant by the following terms: i) Oxidising agent: ii) Displacement reaction: iii) Electronegativity i) Oxidising agent: An oxidising agent is a reagent, either an element or compound that oxidises another species by removing and taking electrons from it and thus are themselves reduced. We know that reduction is gain of electrons, therefore something which accepts electrons is said to be an oxidising agent as it is causing the reactant it is accepting electrons from to be oxidised, in which that reactant in question loses electrons in a reaction. It is the non-metals which tend to be oxidising agents such as F2, Cl2, O2. Oxidising agents are seen within redox reactions -in which reactant elements are both oxidised and reduced, effectively the charge on the elements is altered when the element possess an altered number of electrons when products. Oxidising agents are electron acceptor. The halogens are very good oxidising agents due to their ability to accept electrons to form ionic halides, elements such as the group 7, halogens, possess seven valence electrons, and are very keen to accept a further electron in their outer shell, this makes them excellent oxidising agents which possess high electron affinities. ...read more.


If a reaction was attempted where a less reactive element is placed with a compound which contained an element which was more reactive than that element then no displacement-(replacement) would occur, no reaction would take place. The reason for this would be that the element in the compound would be higher up in the reactivity series than the other element attempting to react with the compound, so will keep its position, bound in the compound. In the case of the non-metal halogens, reactivity would be higher ascending further up the group. In general, a halogen will always displace the ion of a halogen below it in the group. This will be further considered in due course. In other words, generally a more reactive element will displace a less reactive element from it compound, and when this happens a displacement reaction would have occurred. iii) Electronegativity Electronegativity is the ability of an atom to attract bonding electrons in a covalent bond; it is a measure of the tendency of an atom to attract a bonding pair of electrons. Electronegativity increases towards the top right of the periodic table, with the halogen of group 7, fluorine, exhibiting the most electronegative atoms, nearing 4.0 on the Pauling scale, (Noble gases due to their inert, unreactive properties generally are not assigned a value as they generally never form covalent bonds, with the exceptions of Krypton and Xenon). ...read more.


When bonds form between atoms which possess an equal level of electronegativity there will be no discrepancy in the bond to one side over the other, each will exhibit the same forces of attraction on the bonding pair of electrons, which means that the bonding electrons are shared equally between atoms, which results in the bond exhibiting non-polar properties. The bonding electrons will reside 'in between' the atoms with a uniformly formed electron cloud being apparent as both atoms of the bond have the same tendency to attract the bonding pair of electrons. In a chlorine molecule, which possesses two atoms covalently bonded, a pure covalent bond is created, which is generally formed when two of the same atoms combine covalently. Two chlorine atoms each with a value of 3.0 electronegativity on the Pauling scale, on average, have an equal ability to attract the bonding pair of electrons. Essentially the take home message is that: no electronegativity difference between two atoms leads to a pure non-polar covalent bond. A small electronegativity difference leads to a polar covalent bond and a large electronegativity difference between two atoms leads to an ionic bond. Electronegativity is determined by the same general factors which determine ionisation energy. It increases as the number of protons in the atoms increases, it decreases when the number of shielding electron increases, and it decreases when the atomic radius, (the distance of outer electrons to the nucleus) increases. ...read more.

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