Ionic Bonding and Electrolysis Flashcards
What is an ion?
A charged particle
What do atoms try to achieve when reacting?
A full outer shell of electrons/ stable electronic structure
What are positive ions called?
Cations
What are negative ions called?
Anions
Where does ionic bonding take place?
Between a non-metal and a metal
What happens in the ionic bonding process?
Metal atom transfers electrons (to get stable electronic structure) to form a positive ion and non-metal gains them to form a negative ion.
What does an oxidation reaction involve?
A loss of electrons
What does a reduction reaction involve?
A gain of electrons
In terms of half equations, what type of reaction does a metal undergo in ionic bonding?
Oxidation
In terms of half equations, what type of reaction does a non-metal undergo in ionic bonding?
Reduction
What is a giant ionic crystal lattice structure?
A solid, regular arrangement of millions of ions where there are very strong electrostatic forces of attraction between oppositely charged ions, in all directions
What are the properties of a Giant Ionic Structure?
- High melting points and boiling points
- Semi-conductors
- Can be brittle and not shatter proof
What is the structural name of metal and non-metal compounds?
Giant ionic crystal lattice
What type of diagram is used to show the arrangement of ions and/or atoms?
Dot and cross diagram
What is the empirical formula?
A formula used to show the ratio if different elements in a compound
Why do giant ionic crystal lattice structures have high melting and boiling points?
The structure has lots of strong ionic bonds which need a large amount of energy to overcome the attraction and break them
Under which conditions do ionic compounds conduct electricity? Why?
- When molten: Ions are free to move and they’ll carry electric current
- When dissolved in water: The ions are separated and free to move in the solution so they’ll carry the electric current
What are the two ways in which giant ionic lattices can be represented?
- Using a giant 3D giant ionic crystal lattice structure model
- Using the ball and stick giant ionic crystal lattice structure model
What are the advantages of the giant 3D giant ionic crystal lattice structure model?
- It shows the regular arrangement of ions/regular pattern
- Shows the relative size of the ions
What are the disadvantages of the giant 3D giant ionic crystal lattice structure model?
-You can only see the outer layer of the compound
What are the advantages of the ball and stick giant ionic crystal lattice structure model?
- Shows the 3D regular arrangement of ions in the lattice
- Shows that the crystal extends beyond what is shown in the diagram
What are the disadvantages of the ball and stick giant ionic crystal lattice structure model?
- May not show the relative size of the ions
- Shows gaps between ions when in reality, there are none
Define electrolysis:
The splitting up of an ionic compound (into it’s elements) using electricity
What is an electrolyte?
a mixture of ions which can conduct electricity
What happens during electrolysis in principle?
An electric current is passed through an electrolyte. The ions in the electrolyte move towards the electrodes where they react and the compound decomposes
To which electrode do the positive ions move towards during electrolysis?
The cathode (negative electrode)
To which electrode do the negative ions move towards during electrolysis?
The anode (positive electrode)
What occurs at the cathode during electrolysis?
The anions gain electrons from the cathode which has surplus electrons. They are reduced
What occurs at the anode during electrolysis?
The cations lose lose electrons to the anode which is short of electrons. They are oxidised
What happens as the ions gain or lose electrons at the electrodes during electrolysis?
They form the uncharged element and are discharged from the electrolyte
What materials are electrodes made from?
- Metals such as Platinum as it is inert
- Graphite as it is cheap and a good conductor
From which ore is aluminium extracted from by electrolysis?
Bauxite- contains aluminium oxide, Al2O3
Aluminium oxide has a very high melting point (2000), what is it mixed with to reduce its melting point for electrolysis?
Cryolite - lowers melting point to around 950
What happens to the positive aluminium ions once the electric current is passed through the electrolyte?
They are attracted to the cathode (negative) and pick up three electrons and turn into neutral aluminium atoms. These sink to the bottom of the electrolysis tank
What happens to the negative oxygen ions once the electric current is passed through the electrolyte?
They are attracted to the anode (positive) and lose two electrons. The neutral oxygen atoms will then combine to form 02 molecules.
Why does the carbon anode in the aluminium extraction process need to be replaced regularly?
Because it reacts with oxygen to produce carbon dioxide
What are disadvantages of metal extraction from ores using electrolysis?
It is expensive (continues supply of electricity and heating costs) and enhances the greenhouse effect with the production of carbon dioxide
What is the test for chlorine production?
-Chlorine bleaches blue litmus paper, turning it white
What is the test for hydrogen production?
- Hydrogen will make a “squeaky pop” with a lighted splint
What is the test for oxygen production?
-Oxygen will relight a glowing splint
What ions are present in an aqueous solution which is ready for electrolysis?
Negative ions: -That of the dissolved ionic compound -Hydroxide Positive ions: -That of the dissolved ionic compound -Hydrogen
What is produced at the cathode in an electrolysed aqueous solution?
That which is the least reactive
What is produced at the anode in an electrolysed aqueous solution?
If a halide ion is present, then chlorine, bromine or iodine will be formed (halides).
If no halide ions are present, then the hydroxide ions are discharged and oxygen and water will be formed
What are delocalised electrons?
- Free electrons
- which are not attached to a particular atom
- and don’t orbit an atom in an energy level
What makes an ionic bond stronger?
The more electrons that are transferred, the stronger the forces of attraction
What is an ionic bond?
the electrostatic attraction between oppositely charged ions acting in al directions
Describe how an ionic bond forms between potassium and iodine?
- potassium transfers 1 electron to form a potassium metal cation
- iodine gains the electron transferred by the potassium forming the non-metal anion
- the positive and negative ions are held together by forces of electrostatic attraction between the oppositely charged ions acting in all directions
what is a molten salt?
a compound that is melted using heat which separates it into its ions
what is a dissolved salt?
a compound that is dissolved in water which separates it into its ions
What is discharge?
the reaction which happens at electrodes where the elements or compounds are formed
Why can a rechargeable cell be recharged?
Chemical reaction within the cell is reversible
What makes something an alkaline fuel cell?
If it contains hydroxide ions
