chemistry 2.1 chemical bonding

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properties

Different materials have different properties. the property of a material describes the way it behaves.

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Metallic bonding

metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. the mettallic.the force of attraction between these electrons are free to move called DELOCALIZED and the lattice of the metal ion, these usually are strong and have high boiling and melting points.

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Metallic bonding

metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. the mettallic.the force of attraction between these electrons are free to move called DELOCALIZED and the lattice of the metal ion, these usually are strong and have high boiling and melting points.

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Properties of metal

Strong, malleable and ductile, high mellting point and boiling points, good conductors of electricity and heat, lustrous, dense, form oxides when they react with oxygen.

Explanation

Good Conductors of electricity - the "free" electrons are able to move throughout the structure and carry charges.

High melting point - the high melting point of the metals shows that the metallic bonding in metal are strong, therefore lots of energy is needed to break the bonds

Good conductors of heat - the metal ions in lattice are packed closely together and the free electrons can carry kinetic energy through the lattice 

High density - the way that the metal atoms bond together gives them a high density

Malleability - metals can be hammered into shapes. the layers of the ions cna slide over each other in order for this to happen

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How do atoms of different elements chemically bond

There are two ways that atoms of differne elements can join together when forming compounds. these are called ionic bonding and covalent bonding. the type of bonding used gives the compounds and properties 

It is easy to decide whether a compound is bonded using ionic bonding or covalent bonding. you just have to decide whether it is made up of metal and non-metal (ionic) pr two or more non-metals (covalent). you can use the periodic table to find this out. Remember the metals and non-metals are seperat

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Ionic bonding, covalent bonding

This is the bonding that occours between non-metal and metal. the metal transfers an electron(s) from its outer shell to the outer shell of the non-metal in order to obtain a full outer shell of electrons. During the process the metal aton becomes a postive metal ion and the non-metal atom becomes a non-metal ion. 

Covalent compounds are formed whe natoms share electrons. It is very difficultt for some atoms to complete their outer shell by losing or gaining electrons therefore some compounds need to share electrons in order to fill their outer shells. Covalent compounds are formed when two or more non-metal- atoms share pair(s) of electrons 

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ionic structures

Compound containing ionic bonds are said to have giant ionic structuers. they contain millons of ions bonded together to form a crystal lattice. the ions are strongly attracted to each other and are held together in a regular three-dimensional lattice by the electrostatic forces, therefore ionic compounds have high melting and boiling points.

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Q&A of ions

What is an ion?

An ion is a charged species formed when an atom has lost or gained an electron

How are ionic bonds formed?

The metal atom transfers an electron from its outer shell to the outer shell of the non-metal in order to obtain a full outer shell of electrons 

Magensium oxide and sodium chloride both bond by ionic bonding. Magnesium oxide has a higher boiling and melting point than sodium chloride. Explain.

There are more outer shell electrons present in magnesium than sodium so therefore form a 2+ ion as oppose to a 1+ ion the oxide ion forms a 2- ion as opposed to 1- chloride ion. Due to the greater charges carried by the magnesium and oxide ion there are stronger attractive forces between ions, therefore more energy to melt the magnesium oxide

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Properties of covalent molecules

Compounds that contain bonds are said to hav esimple covalent structures. the bonds within the molecule are strong and require a lot of energy to break them; however these substances have low melting points and boiling points because the bonding between molecules ("intermolecular bonding") is very week; simple covalent structures generally exist as gases or liquids. They are soluble in water (carbon dioxide gives fizzy drinks its fizz!). They do not conduct electricity because there are no free electrons or ions to carry charge.  

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Smart Materials

Smart materials are new materials with properties that change reversibly with a change in the material's surroundings. There are several different types:

Shape memory polymers                                                                                                                                                             When these are heated the polymer softens and it can be stretched or deformed. on cooling it remains in the deformed state, but when re-heated it regains its original shape, to which it returns. This is called "shape retenation". uses are plastic car bodies that recove shape on gentle heating and medical sutures that will automatically tighten to the correct tension 

Thermochromic paints pigments                                                                                                                                          These materials can change in colour with changing temperature. Applications already in production are T-shirts and coffee mugs.

Photochromic paints and pigments                                                                                                                    These materials change colour with changing light intensity. Uses are sunglasses that go darker in bright light,jewellery and paint for cars 

  

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