Unit 1 - Topic 5 - Bonding, Structures, and Properties Flashcards
Describe classification
When substances that have similar properties are grouped together.
How many different types of bonding are there?
3
What are the different types of bonding?
Metallic Bonding:
Only found in metals
Ionic Bonding:
Found in compounds made from metals and non-metals
Covalent Bonding:
Found in substances made only from non-metals.
Found in both elements and compounds.
Which non-metallic elements don’t have covalent bonding and why?
Noble Gases
These elements cannot form bonds and exist as single atoms. They are described as MONATOMIC.
What kind of information can testing for conductivity provide?
Useful information about the type of bonding in a substance.
Whether a substance is a solid, liquid or dissolved in water to form a solution can affect the substance’s conductivity.
Conclude conduction and solids
The only solids which conduct electricity are metals and carbon in the form of graphite.
The solids which conduct electricity all have metallic bonding EXCEPT carbon (graphite) which has covalent bonding.
Conclude conduction and liquids
The only liquid at room temperature which conducted electricity was mercury.
Mercury has metallic bonding.
Apart from mercury, all the liquids at room temperature have covalent bonding.
The only melted solid which conducted was lead(II) bromide.
Lead(II) bromide has ionic bonding.
Conclude conduction and solutions
The only solutions which conducted electricity contained an ionic compound.
When does metallic bonding conduct electricity?
When solid or liquid
When does ionic bonding conduct electricity?
When liquid or in solution
When does covalent bonding conduct electricity?
Never except carbon in the form of graphite
What are ionic compounds made of?
Ions not neutral atoms
What happens during conduction?
The ions move to the electrodes of opposite charge.
When the ions touch the electrodes they get changed back to atoms.
This reaction is called ELECTROLYSIS.
Why do ionic compounds only conduct when molten (liquid) and in solution?
Because their ions are FREE TO MOVE ABOUT. When solid the ions cannot move.
What is electrolysis?
The breakdown of an IONIC COMPOUND using electricity.
The reaction occurs on the electrodes during conduction.
What are the atoms in a metal held together by?
Metallic bonding
Are metals affected by conducting electricity?
No
Describe the structure of metals
The atoms in a metal are packed very close to each other.
This allows the electrons on the outer energy level of each atom to move between the atoms
Describe conduction in metals
During conduction, electrons are pushed in from the negative terminal of a battery or power supply
Electrons move towards the positive terminal.
When a METAL conducts the charged particles which move as the current are ELECTRONS.
What does conduction involve?
The movement of charged particles
Describe conduction in ionic compounds
When an IONIC COMPOUND conducts the charged particles which move as the current are IONS.
How are ions formed?
When one or more electron(s) transfers from one atom to another.
The atom which loses electron(s) forms a positive ion.
The atom which gains electron(s) forms a negative ion.
What is the valency of an atom?
The size of the charge on its ion
What do metals form?
Metal atoms always form positive ions. Their atoms lose electron(s).
What do non-metals form?
Non-metal atoms always form negative ions. Their atoms gain electron(s).
What does the valency of an atom tell us?
The number of unpaired electrons in the outer energy level.
What is the only property that has been studied?
Conduction of electricity
What properties depend on the type of bonding in a substance?
Solubility
Melting Point
Boiling Point
Are metals soluble or insoluble?
All metals are insoluble in water and other liquids.
Describe the melting and boiling points of metals
Metals have high melting and boiling points and are solids at room temperature. Mercury is the only exception.
Describe the melting and boiling points of ionic substances
Ionic substances have high melting and boiling points and are all solids at room temperature.
Describe the melting and boiling points of covalent substances
Covalent molecular have low melting and boiling points and can be solids, liquids or gases at room temperature.
Covalent network have high melting and boiling points and can only be solids
If a substance is a liquid or gas at room temperature, it will probably have covalent bonding. The Noble Gases and mercury are exceptions to this general statement.
Describe the solubility of substances with metallic bonding
Insoluble in water
Insoluble in other covalent liquids
Describe the solubility of substances with ionic bonding
Soluble in water
Insoluble in other covalent substances
Describe the solubility of substances with covalent bonding
Insoluble in water
Soluble in other covalent substances
State the different ways in which atoms can bond
Transferring electrons –> ionic bonding
Sharing electrons –> covalent bonding
Describe covalent bonding
In covalent bonding non-metal atoms share electrons. This gives each atom access to the other atom’s outer electrons to fill their outer energy level.
The positive nuclei are attracted to the negative shared pair of electrons. This attraction holds the atoms together. This is the covalent bond.
Why do atoms bond?
In order to get a stable electron arrangement – an electron arrangement similar to a Noble Gas atom.
Metal atoms achieve stability by losing their outer electrons and forming positive ions.
Non-metal atoms achieve stability by:
sharing electrons with other non-metal atoms and forming covalent bonds.
Which substances have different structures?
Covalent and ionic substances have different structures which explains why they have different properties.
Describe the structure of ionic substances
The regular repeating pattern of ions is called an IONIC LATTICE.
Each positive ion is surrounded by 6 negative ions and vice versa.
There are equal numbers of negative and positive ions in the ionic lattice.
The formula of an ionic compound gives the ratio of the ions in the lattice.
The strong attraction between the ions takes a lot of energy to break.
This is why all ionic compounds have high melting and boiling points and are solids at room temperature.
Describe covalent molecular structures
Covalent substances which have low melting and boiling points are made from MOLECULES.
The formula of a molecular substance actually tells you the type of atoms and how many of each atom is in the molecule.
The atoms in a molecule are held together by strong covalent bonds.
There are only weak forces of attraction BETWEEN MOLECULES.
This means little energy is needed to make molecules move away from each other.
This is why the melting and boiling points are low.
Describe molecules
A MOLECULE is a group of non – metal atoms joined together by covalent bonds.
The smallest molecule is made from two non - metal atoms. The largest are made from thousands of non – metal atoms.
Describe covalent network structures
Some covalent substances have very high melting and boiling points and are very hard solids.
These covalent substances are not made from molecules.
They have a structure called a COVALENT NETWORK.
Every atom is bonded to 4 other atoms which builds up a huge network of atoms.
To melt the network requires the strong covalent bonds to be broken.
This means a huge amount of energy is required and the melting point is very high.
Describe electrolysis of a liquid
For electrolysis to take place the ions in an ionic compound have to be free to move. The ions are free to move when the ionic compound is dissolved in water and when it’s molten (liquid).
Describe what happens during electrolysis
A metal forms at the negative electrode as metal ions are positively charged and are attracted to the negative electrode.
A non - metal forms at the positive electrode as non - metal ions are negatively charged and are attracted to the positive electrode.
During electrolysis the ions turn into atoms when they touch the electrodes.
What is electrolyte?
A liquid which contains ions is called an ELECTROLYTE.
Electrolytes conduct electricity.
All ionic compounds make electrolytes when melted or in solution.
Are covalent substances attracted to electrodes?
Covalent substances do not conduct as molecules are not charged, and therefore do not get attracted to the electrodes.
Describe direct current
Electrolysis will only take place when a DIRECT CURRENT (d.c.) is passed into an ELECTROLYTE.
A direct current ensures that there is a POSITIVE and NEGATIVE electrode. [ANODE and CATHODE.]
There is another connection on the power pack - ALTERNATING CURRENT (a.c.).
In a.c. the current changes direction 50 times per second, so there is not a permanent positive and negative electrode. As a result, electrolysis does not occur when a.c. is used.
