Introduction The oxides across the the elements in period period 3 consist consist of metal and non-metal. When going across period 3, the melting point and boiling point of the oxides will vary based on the chemical bonding and the structure of the oxides. The trend in the structure of the oxides is from the metallic oxides containing giant structures of ions on the left of the period, then a giant covalent oxide (silicon dioxide in the middle to molecular oxides on the right. !s for electricity conductivity, none of these oxides have any mobile electron in their solid state, therefore they are unable to conduct electricity. "owever, the ionic oxides are able to conduct electricity in their molten state and undergo electrolysis electrolysis as the movement of the ions towards the electrodes and discharge of the ions when they got there. The acid-base behavior of the oxides can be determined with various reactions. #enerally, the metal oxides will be strongly basic and will have a gradual decrease in p" when going across the period from left to right, via an amphoteric oxide (aluminium oxide in the middle, until it reaches the non-metal oxides with strongly acidic property. $ome simple tests and observations were carried out to %nd out the di&erences between the di&erent types of oxides and to account for these di&erences. 'aterials $odium eroxide, eroxide, 'agnesium )xide, hosphorus(* hosphorus(* )xide, $ilicon(I* )xide, $odium $ulphite, +onc. $ulphuric !cid, niversal Indicator, istilled Water !pparatus Test Test Tubes, Tubes, Thermometer, Thermometer, Test Tube Tube $topper, #lass od, od, Test Test Tube Tube ac/, 'easuring 'easuring +ylinder, 0i1uid ropper, 0-Tube 0-Tube rocedures (! !ppearance The oxide oxide samples were were examined and the following following properties properties were were noted in a larger larger table 2. (a Whether it is a solid, li1uid, li1uid, or gaseous gaseous (b Its colour colour (If any any (4 )n mixing with water 5ive test tubes were set up side by side. 6 m0 of distilled water was poured into each test tube. ! thermometer was placed in the %rst test tube. The temperature was noted. "alf a spatula-tip of sodium peroxide was then added and stirred carefully with a glass rod. The following observations observations were noted, noted, -
The te temperature Whet Whethe herr the the soli solid d has has diss dissol olve ved d !ny other other obser observatio vations. ns. 7xampl 7xample, e, were were ther there e any gaseous gaseous evolved evolved at any any time8 time8
The p" of the solution was tested using a universal indicator. The steps above starting from 9"alf a spatula-tip of sodium:.; were repeated by replacing sodium peroxide, in turns, with magnesium oxide, silicon(I* oxide and phosphorus(* oxide. (+ reparation of $)< gas. ! little concentrated sulphuric acid were added to half a spatula-tip of sodium sulphite in a test tube. The sulphur dioxide was then 1uic/ly bubbled through the water in the %fth test tube. The p" indicated was noted using a universal indicator.
esults iscussion
Structure and Bonding, Melting Point and Boiling Point The physical properties of the oxides vary across eriod 3 elements. #oing across period 3, $odium peroxide, magnesium oxide and aluminium oxide will have a giant ionic structure containing metal ions and oxide ions. Their bonding consist of ionic bond as the metal(=a, 'g, !l with low ioni>ation energy loses their electron and becoming positively charged, coming together with the non-metal () with high electron a?nity where it gains electron becoming negatively charged to form a strong electrostatic attraction between each other. The positively charged ions and negatively charged ions will come attract each other by the strong electrostatic force, forming ionic bonds between the ions. ue to the strong electrostatic attraction between the positive and negative ions in the compound, a lot of heat energy is needed to brea/ the bonds. Therefore they will have a very high melting point and boiling point , and they will exist as solid at room temperature. In $odium eroxide, the sodium atom has an electron arrangement of @=eA 3s and the oxygen atom will have an electron arrangement of @"eA
!ccording to Table 2.<, the melting and boiling point of sodium peroxide is signi%cantly lower than magnesium oxide and aluminium oxide. 5irstly, this is due to the strength of an ionic bond is proportional to the charge on the ions (+oulombEs 0aw. 'agnesium ion has a C< charge in 'agnesium )xide but $odium ion only has a C charge in $odium eroxide Therefore, a higher charged ionic compound will have stronger bonds which will re1uire more heat to brea/ down the bonds. $econdly, there is double bond presence in the !luminium )xide when compared to $odium eroxide which only has single bond. ouble bonds will re1uire more heat energy to brea/ the bonds as they have higher bond energy. =ext, as we go across the period, there isnEt enough electronegativity di&erence between silicon and oxygen to form ionic bond. $ilicon ioxide will form covalent bonds and have a giant covalent structure. The melting point and boiling point for $ilicon ioxide will be very high because the giant covalent structure re1uires large amount of energy in order to brea/ the covalent bonds between the atoms in the molecules. The 0ewis structure for $ilicon ioxide is as belowF .. .. F $i FF ) FF $i F hosphorus entoxide, $ulphur ioxide and +hlorine(I )xide consist of non-metal and oxygen atom. They will form covalent bonds between the non-metal and oxygen atoms, and they will have a simple molecular structure which is held strongly with intermolecular *an er Waals forces. *an der Waals forces are relatively wea/ compared to chemical bonds. 4ecause of the *an er Waals force that is holding one molecule to its neighbor molecule, they will have lower melting and boiling points when compared to the ionic bonded oxides li/e 'agnesium )xide. 'any of them will exist as li1uid of gaseous state at room temperature. hosphorus has an electron arrangement of @=eA 3s < 3p3. It will use all %ve of the valence electron to form bonds with oxygen atom, having 3 electrons forming single bonds with 3 oxygen atom and the remaining < electrons forming a double bond with oxygen atom. The structure of B)D is as below.
$ulphur has an electron arrangement of @=eA 3s < 3pB. 4ecause of the empty d orbital in sulphur, it will allow sulphur to have more than G electron in its valence shell, bypassing the octet rule con%guration. $ulphur will form < double bonds with < oxygen atoms, the 0ewis structure for $ulphur ioxide is shown below. .. .. .. F) F F $ F F )F
+hlorine has an electron arrangement of @=eA 3s < 3p6. Two +hlorine atom will Hust simply form covalent bond with an oxygen atom by sharing one of their valence electron with one of the valence electron from oxygen. )verall, we are able to see that the change in structure and bonding of the period 3 oxides. #oing across period 3, the structure of the oxides changed from #iant Ionic $tructure to #iant +ovalent $tructure and then to the $imple 'olecular $tructure. The type of bonding changes from Ionic bonds to +ovalent bonds. If we were to relate the trend in the change of structure and bonding that ta/es place across the period, it would be almost the same in terms of bonding changes except for sodium, magnesium and aluminium. They will have a metallic bonding instead of ionic bond since there is no formation of ions and transfer of electrons. Their structure would also be metallic structure instead of giant ionic structure. 5or the rest of the elements in period 3, they are most li/ely having the same trend as the oxides across period 3.
Electrical Conductivity =ext, the electrical conductivity of the oxides in their li1uid state will also vary across the period. $odium eroxide, 'agnesium )xide and !luminium )xide will be able to conduct electricity in their moltenli1uid state as they will have mobile ions to undergo electrolysis. $ilicon ioxide, hosphorus entoxide, $ulphur ioxide and +hlorine(I )xide will not be able to conduct electricity as they do not have mobile electrons in their solid or molten state.
Action in water The oxides of eriod 3 will have di&erent reaction as they are dissolved in water. $odium eroxide reacts vigorously in water. $odium peroxide is normally used as a bleaching agent. "ere, it reacts with ice-cold water to form hydrogen peroxide, "<)<. =a<)<(s C <"<)(l J <=a)"(a1 C " <)<(a1 This is a violent exothermic reaction which will cause the "<)< to brea/ down to further water and oxygen gas, causing the glowing splint to burst into Kames. 'agnesium )xide will react with water to form 'agnesium "ydroxide which exhibits only slight solubility in water.
'g)(s C " <)(l J 'g()"<(s This reaction is highly exothermic. !luminium )xide is insoluble in water. The ions in the compound are held too strongly in the solid lattice to react with the water. because of the di?culty of brea/ing up the giant covalent structure. 4ut when we were conducting the experiment, we noticed the solution turned cloudy when $ilicon )xide is added into water. !ccording to an internet resource(0enntech.com,
SiO2(s) + 2 H2O(l) <-> H4SiO4(s) This balance contains silicic acid, a wea acid that also !or"s durin# silicon "ineral hydrolysis ($enntech%co", 2&'4)% This "i#ht exlain the obseration in Table *%' when Silicon Oxide is added to water and the solution turns cloudy%
hosphorus entoxide reacts very vigorously with water and can be used as a powerful dehydrating agent. *arious acids are formed depending upon the amount of water used but, in excess water, phosphoric (* acid is formed. (+reative-chemistry.org.u/,
2HOl
Solubility In e!ene The solubility of the oxides in hexane is also means that the solubility of the oxides in organic solvent. !t the molecular level, solubility is controlled by intermolecular forces. That rule is 9li/e dissolves li/e; and it is based on the polarity of the systems. 5or example, polar molecules dissolve in polar solvents (e.g. water, alcohols and non-polar molecules in non-polar solvents (e.g. the hydrocarbon hexane (chem.ucalgary.ca,
!ccording to many textboo/s, a non-polar bond is formed with the di&erence in electronegativity of ND.6. ! polar bond is ranged from D.6 - .O, and an ionic bond is formed when the electronegativity di&erence is P.O. (+hemteam.info,
Acid"base nature, p The trend in acid-base behavior of period 3 oxides is being summari>ed as below. Their acidity increases from left to right, ranging from strongly basic oxides on the left to strongly acidic ones on the right, with an amphoteric oxide (aluminum oxide in the middle. !n amphoteric oxide is one which shows both acidic and basic properties. $odium peroxide, 'agnesium )xide and are strong basic oxides because they contain the oxide ion, ) <- which has a high tendency to combine with hydrogen ions " C from the water molecule to form hydroxide ions, )" -. The reaction between oxide ion and water is as below. Bla bla bla put your equation here. The <- charge oxygen ion attac/s and forms a bond with a partially positive hydrogen atom of the water molecule. The subse1uent brea/ing of the )-" bond produced two hydroxide ions. 5or example magnesium oxide, 'g)(s C " <)(l J 'g()"<(s J 'g
5or example, hosphorus entoxide, B)D reacts with water to give B moles of hosphoric !cid "3)B,that in turn dissociates into dihydrogen phosphate ion and hydronium ion. "3)B(a1 C "<)(l N---P "<)B-(a1 C "3)C(a1 "owever, this theory is unable to explain why $ilicon ioxide has a slight acidic property, because $ilicon ioxide is almost insoluble in water (explained above in $ilicon ioxideEs action of water . Therefore we reacted $ilicon ioxide with a base, which is sodium hydroxide solution, but it must be hot and concentrated. ! colourless solution of sodium silicate will be formed. $i)< (sC <=a)"(a1 -P =a<$i)3(a1 C "<)(l !luminium )xide is amphoteric. It will have reactions with both base and acid. In this reaction, aluminium oxide is showing the basic side of its amphoteric nature.
In this reaction, aluminium oxide is showing the basic side of its amphoteric nature. !luminium oxide reacts with hot, concentrated sodium hydroxide solution to give a colourless solution of sodium tetrahydroxoaluminate.
Throughout the entire experiment, precaution steps are ta/en to ensure our safety while conducting the experiment. )ne of the precaution steps ta/en was to wear gloves and safety googles when handling corrosive chemicals li/e hosphorus entoxide. =ext up, some chemicals li/e $ulphur ioxide have a cho/ing smell, we were extra cautious to not breath in too much of the $ulphur ioxide gas while preparing the it from sodium sulphite and conc hydrochloric acid.
Conclusion
