Chapter 3: Strucutre of materials

Giant metallic lattices- a lattice of positive ions in the sea of electrons.
Giant ionic lattices- a lattice of alternating positive and negative ions. (NaCl)
Giant molecular lattices- a giant molecule making the lattice (Diamond)
Simple molecular lattice- simple molecules in a lattice held together by weak forces. (Chlorine gas)

Metal Crytals

• High density due to dense packing.
• Metals in the lower parts of the Periodic Table have the highest densities since they have higher atomic masses.
• Malleable and ductile- Metals are malleable since the positive ions are arranged in layers which can slide over each other without breaking the structure. Bonds are strong but not rigid.
• Conducts electricity and heat well- mobility of delocalisied electrons helps to conduct electricity and heat.
• Have crystalline structure.

Alloys

• Alloys are formed by mixing molten metals together and allowing them to cool.
• Alloys are stronger than individual metals. This is because the presence of an impurity atom of a different size prevents slipping between the layers making them more stronger.
• Important alloys- Brass- made of zinc and copper and Stainless steel- chromium, nickel and iron.

Ionic Crystals

  
• Ionic compounds form lattices consisting of positive and negative ions.
• There are equal numbers of both types of the ions so the charges balance.
• Ionic compounds are therefore neutral.
• They are hard
• More brittle than metallic crystals. The layers of ions cannot be slid over each other or the lattice breaks due to bringing same charges together.
• Dissolving the ionic lattice in water however breaks up the lattice and keeps ions apart.
• Ions in solution or when ionic compounds are molten (melted) means that the solution can carry a current since the ions are free to move hence can carry current.
• Ionic compounds that don't dissolve in water means that the ionic bonds must be really strong!

GIANT molecular crystals

Graphite, Diamond and Silicon (IV) oxide.

• Giant molecular crystals have strong covalent bonds.
• elements- carbon - diamond and graphite and in compounds- silicon oxide are examples of giant molecular crystals.
• Diamond and silicon oxide have the similar structure.
• Giant molecular crystals have high melting points and are very hard.

Diamond (Carbon form)

• Tetrahedral structure 
• Strong covalent bonds (high bp)
• Rigid and brittle
• No free electrons- doesn't conduct electricity.

Graphite (Carbon form)

• Has free electrons- conducts electricity.
• Carbon atoms arranged in layers which can slip over each other since the layers have weak forces between them (but the carbon atoms have strong covalent bonds)

IMPORTANT

	Diamond		Graphite
	Property	Use	Property	Use
Appearance	Colourless, transparent crystals that sparkle in light	In jewellery and ornamental objects	Dark grey, shiny solid	-
Hardness	The hardest natural substance!	In drill bits, diamond saws, and glass cutters.	Soft- the layers can slip over each other, has slippery feel	In pencils, as a lubricant.
Electrical Conductivity	Doesn't conduct electricity	-	Conduct electricity	Used as electrodes and carbon brushes in electric motors (physics ain't it :P)

Allotropy- When an element can exist in more than one structural form in the same physical state. Like carbon exists as diamond and graphite and both are solids at room temp.

Allotropes-different forms of the same element.

Chapter 3: Bonding

Diatomic Molecules-a molecule containing two atoms like Cl2 for example.
Bonding- Force of attraction between two atoms.
Ions- Charged particles made from an atom by the gain or loss of electrons to gain stability like the sodium atom will lose one electron to achieve a noble gas arrangement 2,8 (before 2,8,1). This will have a sign Na+ (+ sign on top)
Lattice- a regular three-dimensional arrangement of atoms, molecules or ions in a crystalline solid.
Metallic Bonding
This happens only in metals. Here the atoms in the metals lose the electrons from their outershell. These electrons become delocalized and the atoms become positively charged ions. This hence forms an electrostatic force between the regular array of +ve metal ions and the sea of delocalized electrons within a metal solid.
Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalized electrons.

• The delocalized electrons can move freely therefore metals can conduct electricity.
• This electrostatic attraction is so strong that metals have high mp and bp.
• The +ve ions are arranged in layers which can slip over each other making metals malleable and ductile.
• Metallic bonding results in giant metallic lattices.

Non-metals + Non-metals= Covalent Bonding

• Non-metals combine together by sharing pairs of electrons. This is known as a covalent bond. This holds the atoms together. 
• Groups of atoms bonded together in this way is called molecules 
• They don't have any free electrons or ions so they don't conduct electricity.
• This covalent bond is weak and can be easily broken, therefore covalent compounds normally occur as liquids or gases at rtp like chlorine, hydrogen and water.
• Group IV oxides (except carbon dioxide) makes giant molecular lattices like silicon (IV) oxide. These lattices have many strong covalent bonds which make make their melting points very high since a lot of energy is needed to break all of these bonds.
• Group V,VI, VII oxides and CO2 form simple molecular lattice which is simple molecules. These have low melting points since they have less bonds to break.

Non-metals + Metals= Ionic Bonding

 (The two chlorine ions can be written as 2 then the chlorine ion structure as shown, these type of diagrams are always asked in the exam so better practice them like the one above, just show the outershell in these diagrams.)

• An ionic bond is formed between non-metals and metals.
• The metal loses electrons to become a positive ion to attain noble gas arrangement and the non-metal becomes a negative ion by gaining those electrons. 
• So there is a strong electrostatic force between the positive and negative ions. This is the ionic bond.
• Ionic bonds needs a lot of energy to break, therefore ionic compounds have high melting points. They are usually solid at rtp like NaCl (table salt).
• Ionic compounds conduct electricity only when they are molten or dissolved in water, not as a solid. In solids the ions cannot move therefore cannot conduct electricity. Yes, ions conduct electricity in ionic compounds.
• Ionic bonding results in ionic lattices a regular array of alternating +ve and -ve ions like in NaCl.

Formulas of poly atomic ions

Really important to learn these formulas of ions in writing formulas of substances.

Valency	Simple Metal Ions	Simple non-metallic ions		Polyatomic ions
	+ve	+ve	-ve	+ve	-ve
1	Sodium Na+ Potassium K+ Silver Ag+ Copper (I) Cu+	Hydrogen H+	Hydride H- Chloride Cl- Bromide Br- Iodide I-	Ammonium NH4+	Hydroxide OH- Nitrate NO3- Hydrogencarbonate HCO3-
2	Magnesium Mg2+ Calcium Ca2+ Zinc Zn2+ Iron (II) Fe2+ Copper (II) Cu2+		Oxide O2- Sulphide S2-		Sulphate SO42- Carbonate CO32-
3	Aluminium Al 3+ Iron (III) Fe3+		Nitride N3-		Phosphate PO43-

 Summary

More is on the way... keep checking :)

Chapter 3: The Periodic Table

(This is the best of what I could fit. I suggest to use your own periodic table instead :P)

• -Main-group elements- Groups I to 0
• -Alkali Metals- Group I
• -Halogens- Group VII (non-metals)
• -Noble gases- Group 0 (very unreactive)
• -Transition elements- The block of elements between Group II and III
• -The broadest distinction in the table is metals and non-metals. Non-metals are on the right of the thick line while the metals on the left side of the thick line.
• -A metal is an element that does conduct electricity, is malleable and ductile.
• -A non-metal is an element that doesn't conduct electricity and isn't malleable or ductile.
• -A metalloid is an element that have some features of a metal and some features of a non-metal.
• The difference between Metals and non-metals.

Metals	Non-Metals
They are usually solids at rtp except mercury which is liquid at rtp. They have high mp and bp usually	They are usually solids or gases at rtp except bromine which is a liquid at rtp. They have low mp and bp often.
They are usually hard and have high density	Non-metals are softer than metals usually. They have low densities usually.
All metals are good conductors of electricity.	Poor conductors of electricity
Malleable and ductile	Brittle
Grey in colour except gold and sliver, can be polished	Vary in colour, dull (when solid)
Sonorous	Not sonorous

Trends in the Periodic Table

• -Elements in the same group (vertical columns of elements) have the similar chemical properties and physical properties.
• -Elements in the same group have the same number of electrons in their outershell.
• -For main-group elements, the number of the group is the number of electrons in the outershell. For e.g chlorine is in Group VII so it has 7 electrons in its outershell.
• -The period (rows of elements) number tell us the number of shells in the element. Hydrogen in period 1 has 1 shell for e.g.
• -The atomic size of an atom increases down the group (as the number of shells increase) but decreases across a group since the number of electrons in the last orbit increases hence increasing the attractive force between electrons and protons (-ve and +ve) decreasing the size of the atom as a result.
• -Elements become more metallic (ability to lose electrons) down a group and less metallic across a period since the electrons in the last orbit increases so gaining electrons is much easier than losing them all.
• -In metal groups (like group I and group II) the reactivity of the elements increases as you go down the group.
• The most reactive metal is Caesium since Francium is radioactive (metals in Group I in more reactive than the metals in Group II)
• In the group of non-metals, the reactivity of the non-metals increase up the group
• The most reactive non-metal is Fluorine in Group VII.