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General periodicity.

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Periodicity What is periodicity? Periodicity is the study of the trends in chemical and physical properties of the elements and their compounds relative to their positions in the periodic table. The periodic table has been developed over the last 150 years. The basic structure of the table is very closely related to our current understanding of the electronic structure of the elements. However, when the periodic table was first constructed (by Mendeleev, in the 1800's ), the electronic structure of the elements had not been devised. Instead, early forms of the periodic table relied on using the physical properties of the elements known at that time. It must have been a great revelation to the chemists from the early part of this century to realise that there really was such a strong correlation between chemical properties of the elements and their physical structure. The periodic table. An example of a periodic table is given below : The elements in the columns down the periodic table form groups. The major groups are numbered but often the numbers are given as Roman numerals (the first group, the blue column in the above diagram, is referred to as group I etc). ...read more.


2) First ionisation Energy. First ionisation energy is described as the minimum energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous uni-positive ions. For example ; in equation for the first ionisation energy of sodium would be : Na(g) ==> Na+(g) + e- 3) Electronegavitity Electronegativity is defined as the relative ability of an atom to attract the pair of electrons in a covalent bond. For example ; Hydrogen bonds with oxygen to form water through the formation of covalent bonds. At GCSE you will have learned that the electrons within a covalent bond are shared equally between the atoms forming the bond. However, current understanding of chemistry suggests that this is only an approximation. For example in the water molecule, oxygen atoms have a higher effective nuclear charge than hydrogen (oxygen has a more powerful nucleus) and therefore the oxygen atoms in the bond are able to gain a greater share of the electrons in the bond than the hydrogen atoms. ...read more.


Can you spot which element this is? 6) In fact, there is only one other element in the periodic table that is a liquid at room temperature. Which element is this? What block is this element in? The block that an element is in depends on the electronic configuration of the element. Use the exercise provided below to determine the general rule for assigning elements to blocks. (Be careful with this exercise, it is not as easy as it at first might seem!) Exercise. Step 1 Write down the full electronic configuration of the elements - lithium (3), magnesium (12), Chlorine (17) and cobalt (26). Using a periodic table decide which block each element is in, in the periodic table. Step 2 Compare the data above to come up with a theory as to why each element is in its own particular block in the periodic table. Warning - be sure that you take good note of the electronic configuration of cobalt before you decide on your theory. What was your answer? In fact : An element will belong to the block in the periodic table that denotes the highest energy subshell occupied by the element. ...read more.

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