Topic 2 - Bonding Flashcards
What is a cation?
Positive ions that are formed when when metal atoms lose electrons (in ionic bonding it would be a + charge)
What is an anion?
Negative ions that are formed when non-metals gain electrons (in ionic bonding they’d have a - charge)
What is an ionic bond?
An ionic bond is a strong electrostatic force of attraction between oppositely charged ions.
What are most ionic bonds formed between?
A metal and a non metal
What ion will form if a group1/group 2 element lose an electron?
Group 1 = +
Group 2 = 2+
What ion will form if a group 6/group 7 element gain electrons?
.
Group 6 = 2-
Group 7 = -
How are ionic compounds formed?
By the losing or gaining of electrons
What holds ionic compounds together?
Strong electrostatic forces of attraction between oppositely charged ions (ionic bonds)
How is a lattice structure formed?
The strong ionic bonds allow loads (billions) of ions to be packed together in a regular repeating arrangement
What is the polyatomic ion for sulfate?
2-
SO
4
What’s the polyatomic ion for nitrate?
-
NO
3
What is the polyatomic ion for carbonate?
2-
CO
3
What’s the polyatomic ion for hydroxide?
-
OH
What’s the polyatomic ion for ammonium?
+
NH
4
Why do ionic compounds have high melting and boiling points?
Because they’re ionic bonds are held together by strong electrostatic forces of attraction between ions which need a lot of energy to overcome/break.
Why do some ionic compounds have a higher melting/boiling point?
Some ions have more than one charge so these highly charged ions will attract other ions more strongly and more energy is needed to overcome the strong electrostatic forces of attraction
What does a substance need to conduct electricity?
It must contain charged particles
These particles must be free to move
When can an ionic compound conduct electricity ?
When it is in an aqueous solution
Why can’t ionic compounds conduct electricity in a solid state?
Because it is the charged ions that carry the current of electricity and in a solid state these ions are not free to move
However, in an aqueous solution, the ions are free to move and so they conduct electricity
What are anions (negative ions) attracted to?
The positive electrode I.e. the anode
What are cations (positive ions) attracted too?
The negative electrode I.e. the cathode
What is a covalent bond?
A shared pair of electrons
What are covalent bonds normally formed between ?
Non-metals
When do atoms form double bonds?
When the atoms share two pairs of electrons
Why do covalent bonds I.e. hydrogen have low melting and boiling points?
They have weak intermolecular forces which don’t need a lot of energy to overcome break
However the covalent bonds themselves are strong
What is the valency?
The number of covalent bonds formed
I.e. oxygen has a double bond so it has two bonds so it has a valency of 2
Why can’t covalently bonded molecules conduct electricity?
Because in a covalent bond, electrons are shared between two atoms.
The strong forces between the negatively charged electrons and the positively charged nucleus hold the electrons in place
Therefore, the electrons can’t move and the current can’t be carried/flow.
Why do long polymers have higher melting/boiling points than smaller polymers?
Because they have more intermolecular forces
What are the properties of fullerene?
It has weak intermolecular forces between the molecules so it has low melting points
The weak forces also make them soft and slippery
However, the molecules themselves are strong due to covalent bonds
What are the properties of graphene?
It is very light as it’s only one atom thick
However, the covalent bonds make it strong
Electrons are free to move across its surface so it is a good electrical conductor
What are graphite and diamond both examples of?
Giant covalent structures
What are the properties of graphite?
It has 3 covalent bonds creating sheets of carbon atoms (the 3 strong covalent bonds are hard to overcome to so it has high melting point)
Electrons are free to move and are delocalised so graphite is a good electrical conductor (useful for making electrodes)
It doesn’t have covalent bonds between the layers - the layers are held together very weakly which causes the layers to slide past each other
This makes graphite soft and slippery
(So it’s ideal as a lubricating material)
What are the properties of diamond?
Has 4 strong covalent bonds which take a lot of energy to break so it has a high melting point
The covalent bonds also hold the atoms in a rigid lattice which makes diamond hard
(This is why diamond is used to make tools/strengthen cutting tools)
It is an electrical insulator because it has no free delocalised electrons(no free charged particles)
What are the properties of metals?
High melting points (as solids) Shiny (when polished) Malleable High density Good conductors of electricity
What are the properties of non metals?
Low melting points Not usually shiny (as solid) Brittle (hard but breakers easily) - when a solid Low density Poor conductors of electricity
What is metallic bonding?
The electrostatic attraction between the positive metal ions and the negative delocalised electrons
Why do metals have high melting and boiling points?
The electrostatic attraction is strong so it needs a lot of energy to break/overcome
Why are metals malleable?
When you hit the metal, it doesn’t shatter because the layers of ions slide over each other
The sea of electrons holds the ions together so the metal changes shape instead of breaking
Why can metals conduct electricity?
Because it has a sea of delocalised electrons which are free to move
What happens when you apply a voltage/current to both sides of a metal?
The electrons will flow towards the positive side.
This flow of electrons transfers energy and forms an electrical current
Why do some metals have a higher electrical conductivity?
They have a higher number of delocalised electrons
Sodium is a + ion and will contribute one electron to the sea of delocalised electrons
Magnesium is a 2+ ion and will contribute two electrons so it has a higher conductivity
What substances are soluble/insoluble in water?
Most ionic compounds are soluble
A few simple covalent structures are soluble (not a lot)
Giant covalent are insoluble
Metals are insoluble
What is a problem with dot and cross diagrams?
Doesn’t show the structure formed
What are the problems with metallic models?
Doesn’t show that the ions will be vibrating all the time (but does show that metal ions are held in a lattice)
