- Created by: hollie rawlings
- Created on: 13-01-13 13:49
1.1 atoms elements And compounds
All substances are made form atoms. There are around 100 different types of atom found naturally on earth. They can be combined in many ways to create all of the substances we know and love. They are arranged in a periodic table.
Elements have very different properties from one another. some are radioactive and some are metals,liquids and gases (at room temperature)
All atoms have their own symbols. can you name the symbols for all of these elements.
1.2 atomic structure
Now let's look closely at an atom
The protons in the atoms hold a positive charge
The neutrons have no charge at all
The electrons have a negative charge
This means that all atoms have a charge of 0 (they all have the same amount of protons and electrons)
An ion is an atom with a charge so just bear that in mind
Elements in the periodic table are aranged by their atomic number. These are periods.
Groups go down the table and are organised by the properties of the elements, this is to do with how many electrons are in its last shell.
The atomic number is the smaller of the 2 numbers.
NA 23 It wont look exactly like this. This is how many protons are in the element. 23 is the mass number and this is how many protons and neutrons are in the element. This is because electrons don't weigh anything.
Given the atomic mass number we can work out how many protons ,electrons and neutrons are in an atom.
so 11 + number of neutrons =23 this means that sodium has 12 neutrons.
1.3 The arangement of electrons
Follow my instructions
1.Draw a circle and write a capital H inside it.
2.Then place one cross on the circles edge
Congratulations you have just drawn your first electron diagram.
now you can move on the more complicated diagrams
The first layer only holds 2 electrons. (this is the reason helium in in group 0 as it has a full shell of electrons in the last shell)
The second layer holds 8 so does the third and fourth and so on.
Using the notes on the last page you can now draw the electron diagrams.
Now try and draw sodium if it has 11 electrons
So lets look at an example group 1
Group 1 metals are very interesting as they only have 1 electron in the last shell. This makes them very reactive. Type into YouTube potassium and water experiment and you will see what I mean.
anyway they all have similar properties so they produce similar substances when the react.
lithium + water --> lithium hydroxide + hydrogen
sodium + water --> sodium hydroxide + hydrogen
now guess what is next
potassium + water --> ------------------------- + --------------------
1.4 forming bonds
Some atoms really love each other but some aren't really that bothered. Some are compatible with only some elements whilst others will react with almost anything.
When a metal bonds with a non metal the metal atom gives out one or more atoms to the non metal.both atoms become charged particles called ions (do you remember me telling you).
Opposite charges attract each other this means the bond is a strong one. They are called ionic bonds.
When lithium reacts with chlorine it loses an electron making the overall charge +1. however chlorine gains an electron making the overall charge +1. this is how the strong attraction is made.
When 2 non metals bond they share the electrons. No ions are formed. theses bonds are weaker than ionic bonds because of this.
1.5 chemical equations
Chemical equations show the reactants and the products of a reactions. ( I will use a useful reaction to demonstrate)
calcium hydroxide + carbon dioxide -> calcium carbonate + water
sometimes there will only be 1 reactant, this usually suggests a thermal decomposition.
calcium carbonate -> calcium oxide + carbon dioxide
Anyway many people will use a symbol equation to represent this.
CaCO3 --> CaO +CO2
a useful thing to remember is that the capitals represent a new element.
Na + Cl -->NaCl
How many elements in CaCO3?
extra balancing equations
This can be tricky so read carefully
Spot any problems?
On one side there are 2H and 2O and on the other there are 2H and only 1O.
H2 + O2--> 2 H2O
Now there are not enough hydrogen atoms
2 H2 + O2 --> 2 H2O
Now it finally makes sense.
Balance this equation
Ca + O2 --> CaO
That's all for the first chapter, not very complicated.
Just a couple of questions to check your understanding
1. what is the difference between an element and a compound ?
2. what is the overall charge of an atom?
3. how many neutrons does argon contain?
4. draw the electron diagram for lithium if it has 3 electrons
5. what is an ion?
6. balance this equation
H2 + Br2 --> HBr
unit 2 is all about limestone, ( yeah really fun)
The first thing to know is that 90% of limestone is calcium carbonate. We use limestone in construction it makes mortar, cement and concrete. chalk and marble are also types of calcium carbonate too.
The chemical formula for limestone is CaCO3 (ring any bells) it is an ionic compound which means it transfers electrons.
Ca is +2
CO3 is -2
Remember these charges cancel each other out.
CaCO3--> CaO +CO2
CaO = calcium oxide
Rotary lime kilns
To make a lot of calcium oxide we heat limestone in a kiln.
We fill the kiln with crushed limestone and then heat it.
Calcium carbonate forms calcium oxide (solid) and carbon dioxide (gas)
Nitrogen also leaves the kiln as it is uncreative and present in the air anyway.
2.2 reactions of carbonates
Buildings made form limestone suffer very badly from acid rain. limestone reacts with the acid and a gas is given off in the reaction.
carbon dioxide can be tested for. We use lime water to test for it. (calcium hydroxide)
Calcium hydroxide is an alkaline, carbon dioxide is weakly acidic so it reacts with the lime water. In this reaction calcium carbonate is produced.
Carbonates react with acids to give off salt, water and carbon dioxide.
If we put a metal carbonite in a weak hydrochloric acid would we get a positive lime water test? write the equation to prove your point.
2.3 The limestone reaction cycle
Limestone has a reaction cycle ( all of the things mentioned on the other pages are linked)
CaCO3 --> CaO + CO2
name these compounds
CaO + H2O --> Ca(OH)2
name these compounds
Ca(OH)2 + CO2 --> CaCO3 + H2O
That is the limestone reaction cycle
Name the only waste product given off in the reaction
cement and concrete
mortar is calcium hydroxide with sand and water.
cement is made when you heat limestone with clay. other minerals are sometimes added.
concrete is made when you add more sand and crushed rocks to cement.
2.5 limestone issues
here is a list of limestone issues limestone issues
limestone quarrying harms the environment and destroys ecosystems. blasting is used to dislodge the limestone form the ground. This can cause mild earthquakes.
however it does create jobs and start industries like brick making
creates more business for public buildings and facilities
dust settles on crops and it may damage them
more transportation activity may be a worry for parents