Chemistry Draft

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  • Topic: Periodic table, Halogen, Electronegativity
  • Pages : 5 (1776 words )
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  • Published : March 2, 2013
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11 Senior Chemistry Assignment Draft
Term 1
“Elements within a group are comparable at a macroscopic and microscopic level”

Extended Response Task
Mark Sederkenny 11S
Teacher – Mr. Craven
Due Date – 28/02/13
Subject - Chemistry

Good morning/afternoon peers of Senior Chemistry, for this unit our department has been analysing the macroscopic and microscopic properties of elements. Today this speech will analyse, evaluate and conclude whether Elements within a group are comparable at a macroscopic and microscopic level. This speech will take on board the group of the periodic table known as the halogens. On the full periodic table they are seen as group number 17 and consist of five elements – Fluorine, Chlorine, Bromine, Iodine and Astatine although for the purposes of analysis Astatine will be left out of this extended investigation. Most of the halogens exist as simple diatomic molecules like hydrogen is often found as, the halogens are overly reactive and thus exist in nature in ionic bondage such as Chloride ions in seawater and they easily react with the alkali metals to produce compounds like Sodium Chloride and Calcium Fluoride. Physically the Halogens are broken to all three known states of matter uniquely with Chlorine and Fluorine being gases, Iodine being a solid and Bromine being the only other element at liquid form at room temperature other than mercury. Chemically the halogens are all very reactive elements because of their electron affinity and formation which leaves them with -1 electron to fill their shells or orbitals. Back to the argument it is proposed that elements are in fact comparable at a macroscopic and microscopic level and this will be analysed throughout the physical properties of density and boiling point and for chemical properties electron affinity and first ionisation energy. Density is the mass of any matter per unit of volume, for example g/cm3. The density of the halogen group of elements is vastly varied in density and thus comparable because of the different states of matter that each are in. Because fluorine and chlorine are gaseous their densities are very minute while bromine is liquid and gives an exponentially larger density while iodine which appears as solid in room temperature would provide the highest density of the halogens from its solid state and thus atomic bonds are denser. This is shown in a density table in which the trend is seen where further down the group the halogens are denser. Densities of the halogens:

Element (Abbreviation)| Density (kg/m-3)|
Fluorine (F)| 1.696|
Chlorine (Cl)| 3.214|
Bromine (Br)| 7.5|
Iodine (I)| 4930|

This table and graph clearly shows a trend of density further down, concluding that the density increases with the larger atomic number of the halogens and that thus the density of the halogens is comparable from a macroscopic level. The next comparable physical property is the boiling point of the element. The boiling point of a material is the temperature in units that it takes for a liquid form to begin boiling and change state from a liquid into its gas/vapour form. The boiling point for the halogens increases once again, further down the group and is consistent with this for melting and freezing point as well with the larger and more complex the atom or the atom with more electrons in fact. This is visible from the table below showing boiling points for the purpose of giving an example of this consistency.

Melting and Boiling Points of the Halogens:
Element (Abbreviation)| Boiling Point (°C)| Melting Point (°C)| Fluorine (F)| -188| -218|
Chlorine (Cl)| -34| -99|
Bromine (Br)| 59| -4|
Iodine (I)| 184| 116|

From this it is now visible to see that the temperature for boiling point trend is an increase down the group from Fluorine to Iodine with almost one hundred degrees difference. Therefore it is proven to be relative to the group’s...
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