Chemistry Unit 2

Nanotechnology, bonding, catalysts, relative formula mass, protons, neutrons and electrons

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  • Created by: Angharad
  • Created on: 09-11-11 19:45

C2 Chemistry



  • Number of protons changes with each element
  • Positive charge
  • Number of protons displayed in the element box usually above the symbol as the atomic (proton) number e.g. Oxygen's atomic number (protons) is 8...


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  • Neutral charge (I remember this as Neutron sounds like Neutral and they start with the same 4 letters)
  • Number of neutrons affects the properties and radioactivity 
  • The number of neutrons can change an atom into an isotope if it's unstable
  • More neutrons make an atom heavier


  • Negatively charged
  • Can turn any atom/element into an ion 
  • The group number on your periodic table tells you how many electrons are in the outside shell
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Atomic mass

Atomic mass...

The mass of individual atoms as a break down e.g 

CaCO3 (Find out each elements individual relative atomic mass, usually found below the symbol on your periodic table, use your key on your periodic table to help you as some are different!)

Ca - 40

C - 12

O - 16 (x3) 

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Formula mass

Formula mass....

The mass of atoms all together to create compound e.g

Limestone - CaCO3 (add all the relative atomic masses together)

Ca - 40

C - 12

O - 16 (x3) 


Total Formula mass = 100 

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  • Lower energy required for the reaction to take place
  • Aren't impacted by the reaction therefore don't run out or die unless denatured when a catalyst goes over it's optimum tempurature
  • Speed up reactions therefore cost effective in industry
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  • Science of really small particles 
  • Nano = small, 1000th of a mm.
  • Small particles which affect the properties of other materials e.g make them stronger or more resiliant 

Examples of Nanotechnology in Industry and new engineering...

  • Nanotechnology injected into blood to scrape off bad chlosterol build up in our arteries
  • Used in tennis rackets to make them lighter, stronger and more resiliant. 

Type Nanotechnology into google and millions of helpful results will appear informing you on it's uses and the ins and outs. 

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Covalent bonding

Covalent bonding 

  • Non metals only 
  • Strong bonds e.g diamond, the hardest substance and graphite which is in layers, sliding over other layers
  • Not gaining or losing electrons but sharing electrons
  • Neutral charge

In covalent bonding we draw a dot and cross diagram to show the strong bonds between elements, P.T.O to learn how to draw one and what their purpose is!

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How to draw a dot and cross diagram

Here's a dot and cross diagram to represent covalent bonding in Cl2 (Chlorine x2) 


To draw a dot and cross diagram, find out how many electrons are in the outer shell by looking at the element's group so Chlorine is in group 7 therefore has 7 electrons in it's outer shell, (When drawing a dot and cross diagram you only need to draw the outer shell.) The individual Chlorine elements aren't stable if they only have 7 electrons therefore they need to share electrons by creating this strong covalent bond. 

Remember it's a dot AND cross diagram not a dot or cross diagram so draw one of each symbol so as to make a distinction between the different electrons.  

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Ionic bonding

Ionic bonding...

  • Between metals and non metals, changing the charge
  • Gaining and loosing electrons 
  • Ions are held together by electrostatic forces

e.g. Na and Cl (Sodium and Chlorine) Na originally had 11 electrons and Cl had 17, both are odd numbers and unstable so Na gives chlorine one electron making them both stable. 

After Na giving away an electron and Cl gaining one you have to show this by drawing brackets around each dot and cross diagram and then showing how many electrons each element has gained or lost by drawing negative or positive signs outside the bracket. 

This is very confusing as although Na (Sodium) has lost one electron it now has a positive sign by it and even though Chlorine has gained an electron there is a negative sign by it. I just remember it by the opposite of each action which has taken place. If Sodium (Na) had given away 2 electrons it would have a +2 by the bracket etc.


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Metallic bonding

Metallic bonding...

  • Metals only bond with other metals
  • Electrons are delocalised and free so aren't shared or donated 'floating'
  • Metals conduct electricity because the electrons move inside the metal
  • Structure of metals isn't the same throughout
  • Metals are in layers which slide over each other (malleable)


  • Sonorous 'ding' 'dong' the sound you get by tapping two metals together
  • Shiny
  • Malleable (bendy)
  • Solid at room temp except mercury
  • Conducts heat and electricity
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Passing an electric current through ionic substances that are molten or in solution to break them down into elements

  • During electrolysis atoms become ions
  • Positively charged ions move to negative electrode (Cathode)
  • Negatively charged ions move to positive electode (Anode)

Remember opposites attract!

  • During Electrolysis gases may be given off or metals deposited at electrodes
  • Metals form positive ions that move to the negative electrode
  • Precious metals are left in the impurities after Electrolysis
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Acids, Bases and Salts

Acids: Substances with a pH of less than 7, the stronger the acid, the lower the pH number. Acids turn blue litmus paper red and turn universal indicator red if they are strong, and orange or yellow if they are weak.

Bases: pH of more than 7, when they're dissolved in water they're known as Alkali's. Usually metal oxides or metal hydroxides. They react with acids and neutralise them to make a salt and water.

Alkali's: Bases that dissolve in water with a pH of more than 7, The stronger the Alkali the higher the pH. Alkali's turn red litmus paper blue and turn universal indicator dark blue or purple if they're strong and blue/green if they're weak.

Neutral Solutions: pH of 7, water is neutral and they turn universal indicator green but do not affect the colour of litmus paper. 

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