Chemistry C4

Nucleus
1) It's in the middle of the atom
2) It contains protons and neutrons
3) It has a positive charge because of the protons
4) Almost the whole mass of the atom is concentrated in the nucleus

Electrons
1) Move around the nucleus in electron shells
2) They're negatively charged
3) They're tiny, but they cover a lot of space
4) Electrons have virtually no mass

Number of Protons equals the number of Electrons
a) the atomic number tells you how many protons there are (bottom number)
b) To get the number of neutrons subtract the atomic number from the mass number(top)
c) The mass ubmer is always the biggest number

Periodic Table
a) The modern periodic table shows the elements in order of ascending atomic number
b) periodic table is laid out so that elements with similar properties form colums
c) Vertical colums are called groups, the group tells you the number of electrons it has in its outer shell
d) The rows are called periods. These represent the shell number

Isoptopes have an Extra Neutron
Isotopes are different forms of the same element, which have the same number of protons but a dfferent number of neutrons.
1) Isotopes have the same atomic umber but different mass numbers.
2) If they different atomic numbers, they'd be different elements
3) common example: carbon 12 , carbon 14

Electron Cell Rules
1) Electrons always occupy shells
2) The lowest shell are always filled first
3) Only a certain number of electrons are allowed in a shell, 1st: 2, 2nd: 8, 3rd: 8

Electron Configurations

Learn the first 20 from science book!

Ionic Bonding
In ionic bonding, atoms lose or gain electrons to form charge particles which are then strongly attracted to one another.

Shells
1) If an atom has one or two electrons in their outer shell they lose them to have a full shell
2) If it loses an electron it becomes a positive ion
3) Ions are very reactive and will leap at the first passing ion with an opposite charge and stick to it like glue.
4) If an atom has a shell which  is nearly full then they try to fill that shell becoming negative ions.

Ionic Compounds Form Giant Ionic Lattices
1) Ionic bonds form between metals and non-metals and always produce giant ionic structures.
2) The ions form a closely packed regular lattic arrangement. The ions are not free to move though, so these compounds do not conduct electricity when solid
3) There are very strong chemical bonds between all the ions

1) When metals form ions, they lose electrons to form positive ions.
2) When non-metals form ions, they gain electrons to form negative ions.
3) So when a metal and a non-metal combine, they from ionic bonds.
4) The number of electrons lost or gained is the same as the charge on the ion

Covalent Bonds - Sharing Electrons
1) When non-metal atoms combine together they form covalent bonds by sharing pairs of electrons
2) Each covalent bond provides one extra shared electron for each atom
3) Each atom involved has to make enough covalent bonds to fill up its outer shell

Simple Molecular Substances
1) Substances formed from covalent bonds usually have simple molecular structures like COv2
2) The atoms within the molecules are held together by very strong covalent bonds.
3) By contrast, the forces of attraction between these molecules are very weak
4) This results in the melting and boiling points being very low because the molecules can be easily parted
5) Molecular substances don't conduct electricity because there are no free electrons.

Alkali Metals
Includes: lithium, sodium, potassium, rubidium and caesium
a) as you go down group 1, the alkali metals become more reactive because the outer electron is more easily lost as its further from the nuclues so less energy is needed to remove it.
b) the alkali metals all have one outer electron making them very reactive and gives them all similar properties.
c) All have the following physical properties:
-low melting point and boiling point
-low density
-very soft
Oxidation is the loss of electrons
1) When alkali metals are put in watert they react and produce hydrogen
2) Alkali metal compounds burn with the following colours:
Lithium - Red flame
Sodium - Yellow/orange flame
Potassium - lilac flame

Group 7 contains fluorine, chloring, bromine, iodine and astatine.
a) All group 7 elements have 7 electrons in their outer shell so they all react by gaining one electron
b) As you go down group 7, the halogens become less reactive as there's less force to gain an extra electron because it's further away from the nucleus.
c) As you go down group 7 the meting points and boiling points of the halogens increase.
Reduction is the gaining of electrons

Halogens react with alkali metals to form salts
1) More reactive halogens will displace less reactive ones
2) Chlorine can displace bormine and iodine from a soluton of bromide or iodide

Metals have a crystal structure
1) All metals have the same basic properties due to the specia type of bonding that exists in metals
2) Metals are held together with metallic bonds which allow the outer electrons of each atom to move freely

Most have high melting and boiling points, and high density
1) Metals are very hard, dense and lustrous
2) There's a strong attraction between the free electrons and the closely packed postive ions causing very strong metallic bonding.
3) Metals have a high tensile strength in other words they're strong and hard to break
4) They're also malleable
5) Metals are good conductors of heat and electricity because of the free electrons.

Thermal Decomposition

1) Thermal decomposition is when a substance breaks down into atleast two other substances when heated.
2) Transition metal carbonates break down into a metal oxide and carbon dioxide.

Precipitation
1) A precipitation reaction is where two solutions reaact and an insoluble solid forms in the solution

temp hard water 

• contains calcium and or Mg 
• hardness can be removed by boiling  

permanent hard water

• 
  
• hardness can't be removed by boiling 

testing for hardness

by how well the water lathers when soap is added and the water is shaken, its hard to create a lather in hard water, if this changes after water has been boiled its temporary hard water if it doesn't it's permanent hard water. 

boiling removes temp hardness because it converts the hydrogencarbonates of calcium and Mg into carbonates which are insoluble and form a precipitate, this is what forms limescale in kettles. 

• adding sodium carbonate. the calcium and Mg ions bond with the carbonate ions, meaning that less detergent has to be used. This is cheap but deposits still form.
• Passing the water through an ion exchange column. This removes the calcium and magnesium ions and replaces them with sodium ions, which do not cause hardness this is effective but expensive.

Advantages

• Many people think that hard water tastes better than soft water
• Calcium and Magnesium are essential minerals in the diet and hard water can provide them.
• The magnesium in hard water may give some protection against heart disease.

Disadvantages

• Temporary hard water can produce deposits which can clog and damage hot water pipes, boilers and kettle elements.
• Hard water requires more soap or detergent to clean effectively.
• Treating permanent hard water in order to save on detergent can produce deposits on washed clothes.