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Chemistry the Periodic Table and Bonding

By akeemansolia Jun 23, 2012 1472 Words
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 group.

2.Density increases DOWN the group.
3.Ease of Ionisation increases UP the group -As diameter of the atom DECREASES the more easily it GAINS electrons to form ions. 4.Strenght as an Oxidising agent increases UP the group -The more readily an element IONISES, the more readily it REMOVES electrons from other elements. 5.REACTIVITY increases UP the group -Due to INCREASE in ease of IONISATION. Fluorine is the most REACTIVE in GROUP 7. Why does reactivity increase up the group for non-metals?

Answer: Reactivity increases up group for non-metals because non-metals have to gain electrons in order to IONISE. Fluorine IONISES easier than Chlorine because of its smaller size hense the reason Fluorine is MORE REACTIVE than Chlorine. 6.DISPLACEMENT-An element is Displaced from its compounds by an ELEMENT ABOVE it in the group.

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Elements(METALS) - A 2.8.1 , B 2.8.1 ,C 2.8.3 Non-metals have MORE THAN 3 ELECTRONS in their outermost and Metals have LESS THAN 3 ELECTRONS in their outermost. Element A is more REACTIVE than A & C .

It is easier for an atom to lose 1 electron than 2 or 3 electron. The SMALLER the ATOM the easier the atom can GAIN ELECTRONS and become IONS.

Atoms of the elements in GROUP 0 of the Periodic Table the are also know as NOBLE GASES OR INERT GASES Have FULL OUTER SHELLS of electrons.They are STABLE and UNREACTIVE and exist in nature as individual atoms . Atoms of all other elements do not have full outer shekks therefore they are NOT STABLE. THE attempt to gain FULL SHELLS and become stable by: >LOSING ELECTRONS

>GAINING ELETRONS or
>SHARING ELECTRONS.
In doing this atoms BOND with each other. There are THREE (3) TYPES OF BONDING: *1.IONIC IR ELECTROVALENT BONDING -This occurs when a METAL bonds with a NON-METAL. It involves the COMPLETE TRANSFER OF OUTER (VALENCY) ELECTRONS from the Metal atom , or atoms TO the Non-metal atom or atoms. The METAL forms POSITIVE (+) IONS called CATIONS and the NON-METAL atoms form NEGATIVE IONS called ANIONS IONS (-) have full outer shells of electrons . When atom LOSES electrons it becomes Positive (+) in other words it become A CATION which is positively charged . Example Na+ ,Mg2+.

When a atom GAINS electron it becomes Negative in other words it become AN ANION which is negatively charged.Example F- ,S2-

**2.COVALENT BONDING -This occurs when two or more NON-METALS atoms BOND. It involves the SHARING of valency electrons. Covalent bonding results in the Formation of MOLECULES.

**3.METALLIC BONDING-This occurs in metals. The metals atoms are packed packed tightly in ROWS and the valency electrons from each atom are lost to a "Sea" Of ELECTRONS. These electrons are MOBILE and bind together CATIONS formed as a result of the ATOMS LOSING ELECTRONS.

VALENCY is the NUMBER OF ELECTRONS an ATOM has to LOSE ,GAIN or SHARE to attain a STABLE ELECTRONIC STUCTURE. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- SUBJECT:CHEMISTRY

TOPIC: THE SOLUBILITY OF SALTS AND BASES

*ALL SODIUM,POTASSIUM, and AMMONIUM SALT are [ SOLUBLE].
*ALL NITRATES are [SOLUBLE].
*MOST SULPHATES are SOLUBLE [EXCEPT those of BARIUM, LEAD AND CALCIUM]. *ALL CHLORIDES are SOLUBLE [EXCEPT those of SLIVER and LEAD II]. *MOST COMMON CARBONATES are (INSOLUBLE) [EXCEPT those OF SODIUM, POTASSIUM AND AMMONIUM]. *MOST METAL HYDROXIDES are (INSOLUBLE) [EXCEPT those of SODIUM , AMMONIUM AND CALCIUM]. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- TOPIC: CHEMICAL REACTIONS ( ACIDS ,BASES AND SALTS)

1. BASE + ACID ------------>SALT + WATER . This is called called a NEUTRALISATION REACTIPN 2.CARBONATE OR HYDROGENCARBONATE + ACID----------->SALT + WATER + CARBONDIOXIDE 3.REACTIVE METAL + ACID ------------> SALT +HYDROGEN EG. Mg(s) +2HCL(aq) + H2(g) (Acids except nitric acid react with reactive metals) only metals above hydrogen will react with acid.Copper and Silver do not react with acids. 4.ZINC OR ALUMINIUM + ALKALI -----------> SALT + HYDROGEN 5.ALKALI + AMMONIUM SALT ------------->SALT + WATER + AMMONIA

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- TOPIC:LABORATORY PREPARATION AND IDENTIFICATION OF GASES

To prepare Carbon dioxiode (CO2) ACID + CARBONATE------------>SALT + WATER + CARBON DIOXIODE. HCL(aq) + CaCO3(s)---------------> CaCl2(aq) + H2O(l) + CO2(g) Acid+ Carbonate--------------> Salt + Water + Carbon dioxide

To prepare Oxygen (O2) .Decompostion of hydrogen peroxide. Manganese Dioxide (MnO2) is used as a CATALYST: 2H2O2(aq)------MnO2------------->2H20(l)+ 02(g)
Hydrogen peroxide --------MnO2---------->Water + Oxyen

To prepare Ammonia Gas[ NH3 (g) ] . Alkali + Ammonium Salt ----------------> Salt + Water +Ammonia NH4CL(aq) + NaOH(aq)------------->NaCl(aq) + H2O(l) + NH3 (g) Ammonium salt + Alkali-----------> Salt + Water + Ammonia gas.

TOPIC: How to Prepare an INSOLUBLE SALT
METHOD -IONIC PRECIPITATION
Two soluble salts that have the required ions. eg. PbSO4 [(Pb--Pb(NO3)] [ (SO4---CuSO4. Pb(NO3)2(aq) + CuSO4(aq)-------------->PbSO4(s) + Cu(NO3)2(aq)

HOW TO MAKE A SOLUBLE SALT (not NA+, K+ or NH4+)
example magnesium chloride,zinc sulphate,aluminium nitrate,calcium chloride. To make a soluble salt except Na+ ,K+,NH4+.Use :
a) an acid -( anion part)
b) insoluble MOCH---(Metal,Oxide,Carbonate,Hydroxide)-----}cation part
1.Cu SO4 {Cu-CuO,CuCO3,Cu(OH)2} {SO4-H2SO4}
CuO(s) + H2S04(aq)----------- CuSO4(aq) + H20(l)

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