Chemistry the Periodic Table and Bonding

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Subject: Chemistry
Topic: The Periodic Table

The periodic table is a classification of all the elements based on ATOMIC NUMBER. It is composed of HORIZONTAL PERIODS and VERTICAL GROUPS which contain the elements arranged: *the order of INCREASING ATOMIC NUMBER

*in the relation to the ELECTRON STRUCTURE of the atoms
*in the relation to their CHEMICAL PROPERTIES

(Criteria Used For Placing ELEMENTS in the Periodic Table)

1. ATOMIC NUMBER
2. NUMBER OF SHELLS (PERIOD)
3. NUMBER OF OUTER ELECTRONS (GROUP)
4. CHEMICAL PROPERTIES OR (REACTIVITY)

*** PERIODS
They are HORIZONTAL ROWS of elements. There are SEVEN (7) periods numbered 1 to 7 *Elements of the one period all have the SAME NUMBER OF ELECTRON SHELLS. *Going ACROSS a period each element has ONE MORE PORTON and ONE MORE ELECTRON than the previous element. *Going ACROSS a period, the chemical properties of elements becomes LESS METALLIC AND MORE NON-METALLIC.

***GROUPS
These are VERTICAL COLUMNS OF ELEMENTS .These are EIGHT groups numbered I to VII with the final group 0. *Each element in a group has the SAME NUMBER OF ELECTRONS IN ITS OUTER SHELL- for elements in Groups I to VII, this number is the same as the group number. *The COMMON OXIDATION STATE (NUMBER) of elements in the Groups I toe *Going DOWN a group, each element has ONE MORE ELECTRON SHELL than the previous element. *Elements in the same group have SIMILAR CHEMICAL PROPERTIES. *The METAL NATURE of elements INCREASES DOWN THE GROUP.

*The REACTIVITY of the metals INCREASE DOWN THE GROUP.
*The REACTIVITY of the non-metals INCREASES UP a group.

Between Groups II and III are the TRANSITION METALS. All have TWO ELECTRONS IN their outer shell and most exhibit VARIABLE OXIDATION STATES when in compounds.

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TOPIC: GROUP TRENDS IN THE PERIODIC TABLE

*TRENDS IN GROUP II- THE ALKALINE EARTH METALS (GROUP 2)

ELEMENTS - Be (Beryllium)2.2 , Mg (Magnesium)2.8.2 ,CA (Calcium) 2.8.8.2 Sr (Strontium)2.8.8.8.8.4 Ba (Barium)2.8.8.8.8.8.8.4 1.Melting point increases up the group (EXCEPT Mg)
2.They have electrons in the outer shell,Valency is 2 oxidation number +2 3.Metallic nature INCREASES DOWN the group.
4.Going DOWN the group each element has one more electron shell ( when losing ELECTRON it IONISES). 5.REACTIVITY INCREASES DOWN the group. Atoms that ionise or lose electrons easier are more REACTIVE hense the reason reactivity INCREASES DOWN THE GROUP. 6.Ease of Ionisation increases DOWN the group .As diameter of the atom INCREASES the more easily it LOSES valency electrons to form IONS. 7.Strenght as a reducing agent increases DOWN the group, The more readily an element IONISES ,the more readily it GIVES electrons to other elements. 8.Reactivity with oxygen ,water,dilute HCL(aq) and dilute H2S04(aq) increases DOWN the group Due to INCREASE IN THE EASE OF IONISATION. 9.DISPLACEMENT An ELEMENT is displaced from its compounds by an elements BELOW IT IN THE GROUP. 10.STABILITY OF COMPOUNDS increases DOWN THE GROUP.

11.Basic Strenght of OXIDES INCREASES DOWN THE GROUP
12.SOLUBILITY OF HYDROXIDES INCREASES DOWN THE GROUP.
13.Solublity of Carbonares/Sulphates * INCREASE UP THE GROUP.
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* TRENDS IN GROUP VII- THE HALOGENS (GROUP 7 - NON-METAL ELEMENTS ) ELEMENT
F (Fluorine) 2.7[ Appearance and State at room temperature Pale Yellow GAS] , Cl (Chlorine) 2.8.7[Appearance and State at room temperature Yellow-green GAS], Br (Bromine) 2.8.8.8.8.[Appearance and State at room temperature Red-Brown LIQUID ],I (Iodine)2.8.8.8.8.8.8.3 [Appearance and State at room temperature Grey -Black SOLID.] 1.Melting Point/Boling Point increases DOWN the...
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