chemistry

Chemistry Higher tier C2a

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  • Created by: kasia
  • Created on: 10-11-11 18:35

Electronic Structure

Electrons

- electrons fill up the shell closest to the nucleus first,

-when this is full they fill up the next one

-the electronic structure is always 2,8,8

-the last number always tells us what group

it belongs to in the periodic table

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Compunds and Isotopes

Compounds

-compounds are formed when two or more elements chemically react together

-it is difficult to seperate compounds

-Compounds are chemically bonded

Isotopes

-isotopes are different atomic forms of the same element,which have the same numbrer of protons but a different number of neutrons.

Carbon-14 is unstable and it decays into NITROGEN

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Convalent Substances

Simple Molecular Substances

- they form very Strong Convalent Bonds

-The forces of attraction between these molecules are very weak

-Molecular Substances dont conduct electricity

Giant Convalent Structures

-These are similar to Giant ionic structures but they have NO charged ions

-All atoms are bonded to each other by strong convalent bonds

-they do NOT conduct electricty

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Metallic Structures

Metal Properties

- in a metal electrons are free to move so metals are good conductors of heat and electricity.

-These electrons also hold the atoms together in a regular structure 

-They also alow atoms to slide over each other causing metals to be Malleable 

 


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New Materials

Smart Materials

- Smart materials behave differently depending on the conditions

-Dyes change colour depending on temperature or light intensity. 


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DIfferent formula's (1)

Relative Atomic Mass

all you do is add the masses together and it is used to compare the mass of different atoms for example:

Relative Formula Mass 

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Different formula's (2)

Empirical Formula

Method:

1. list the two elements 

2.Write the Experimental masses

3.Divide by Ar

4.Multiply by 10...then divide by 4

Calculating Masses in reactions 

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The Mole

The mole

- number of moles=             mass(g)                       

                                   Relative mass of the substance 

for example:how many moles are there in 42g of Carbon?

no.of moles=mass (g)   =42/12  = 3.5moles

Atom Economy

Total Mr of useful products       

   total Mr of reactants 

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Precentage Yield

Precentage yield

precentage yield= actual yield (g)

                        predicted yield (g) 

The amount of product made in the reaction is called the yield 

we often find that the actual yield is lower then the predicted yield this is because:

-the reacton is reversible and does not go to completion

-some of the products were lost for exmaple during filtering or evaporation

-there may be side reactions that are producting another product 

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