Ionic and Covalent Bonding Flashcards
What is the most stable atoms of the Periodic Table?
The noble gases because they have a full outer shell
What are cations?
Metal atoms that form positive ions
What are anions?
Non-metal atoms that form negative ions
What are most ionic bonds between?
A metal and a non-metal
What is a lattice structure?
A regular repeating arrangement
Why will ionic compounds often form crystals when solid?
Because of their regular lattice structure
What is the charge of ionic compounds?
Neutral - no overall charge
What does polyatomic mean?
Ions with more than one atom, for example ammonium
What are ionic bonds?
The electrostatic forces of attraction between the ions in ionic compounds
What do ionic compounds form?
Crystals
Why must ionic compounds be heated to high temperatures before they change state?
Because a lot of energy is needed to overcome the electrostatic forces of attraction in order to separate the ions to change state
When do ionic compounds conduct electricity?
When they are molten or dissolved in water
When do ionic compounds not conduct electricity?
When they are in the solid state
What are the 2 conditions that must be met for a susbstance to conduct electricity?
- It must contain charged particles
- These particles must be free to move (delocalised)
What does delocalised mean?
Particles that are free to move
When an ionic compound conducts electricity, what carries the current?
The charged ions
What are anions attracted to?
The positive electrode, the anode
What are cations attracted to?
The negative electrode, the cathode
What are covalent bonds usually formed between?
Non-metal atoms
What is the average diameter of an atom?
10 to the power of -10 metres
What is the valency of an element?
The number of covalent bonds formed by atoms of the element (the same number of electrons needed to obtain a full outer shell?
What is the name of the weak forces of attraction between molecules?
Intermolecular forces
What are polymers?
A chain of monomers, which are small, simple molecules
What are allotropes?
Different structural forms of the same element
What are fullerenes?
The simple molecule forms of carbon, in which each carbon atoms is covalently bonded to 3 other carbon atoms
State some properties of fullerenes
- Weak intermolecular forces, so low melting/sublimation points
- Weak forces make them soft and slippery
- Molecules themselves are very strong due to their covalent bonding
Describe some properties of graphene
- Similar to fullerenes, but not a simple molecules
- Consists of a sheet of carbon atoms, but no fixed formula
- Sheet is one atom thick (so lightest material known)
- Its covalent bonds make it extremely strong
- Allows free electrons to move across its surface and so is a good electrical conductor
What are diamond and graphite examples of?
Covalent, giant molecular structures, which have huge 3D networks of carbon atoms linked by covalent bonds
How many covalent bonds does graphite and diamond have for each carbon atom?
Graphite - 3
Diamond - 4
Describe what the 3 covalent bonds for each carbon atom means for graphite
It gives graphite a layered structure and means that not all of its electrons are held in covalent bonds, and these delocalised electrons are free to move and can carry an electrical current, and so is used in electrodes in electrolysis as it conducts electricity well, is cheap and not very reactive
What does the weak forces of sheets of carbon atoms in graphite allow?
The layers to slide past each other, making graphite quite soft and useful as a lubricant
Why is diamond very hard?
It has a rigid network of carbon atoms in a tetrahedral arrangement, joined by covalent bonds, which is why diamond is used for tools to cut things and as al electrical insulator because it has no free charged particles
Name some common properties of metals
- High melting points
- Shiny when polished
- Malleable
- High density
- Good conductors of electricity
Name some common properties of non-metals
- Low melting points
- Not usually shiny when solid
- Brittle when solid (easy to break or snap)
- Low density
- Poor conductors of electricity
What is metallic bonding?
The electrostatic attraction between the positive metal ions and the negative delocalised electrons; this attraction is strong, so metals have high melting/boiling points
When does the electrical conductivity of a metal increase?
As the number of delocalised electrons increases
Name some of the properties of the elements/compounds of ionic bonding
- High melting/boiling points
- Many are soluble in water
- Conduct electricity when a liquid/in solution, but not when solid
Name some of the properties of the elements/compounds of simple molecular (covalent) bonding
- Low melting/boiling points
- Few are soluble in water
- Most don’t conduct electricity
Name some of the properties of the elements/compounds of giant covalent bonding
- High melting/boiling points
- Insoluble in water
- Most don’t conduct electricity (except in carbon as graphite)
Name some of the properties of the elements/compounds of metallic bonding
- High melting/boiling points
- Insoluble in water
- Conduct electricity when solid/liquid
Where is ionic bonding found?
In most compounds containing metal and non-metal atoms
Where is simple molecular (covalent) bonding found?
In most non-metal elements and compounds
Where is giant covalent bonding found?
In a few non-metal elements and some compounds of non-metals
Where is metallic bonding found?
In all metals
What is the problem with dot and cross diagrams?
They don’t show how the structure is formed in covalent bonding and they suggest that the electrons in different atoms are different, when they are actually all the same
What is the problem with metallic models?
They do not show that the ions will be vibrating all the time
What is the problem with 3D ball and stick models?
They show the atoms too far apart and there are not really ‘sticks’ holding the atoms together
