Structure and bonding Flashcards
(22 cards)
What’s ionic bonding?
What happens to the metal and non metal atoms electrons?
Metals and Non Metals reaction.
Metal atom loses electrons to form positively charged ions.
Non metals gain electrons to form negatively charged ions.
They’re strongly attracted due to electrostatic forces.
Holds ions to create an ionic compound.
What type of diagram shows how ionic compounds are formed?
Dot and cross diagrams shows how electrons are arranged in an atom or ion.
What structure is an ionic compound?
Giant ionic lattice.
Held together by strong electrostatic forces of attraction between oppositely charged ions.
What properties do all ionic compounds have?
-High melting and boiling points due to lots of energy needed to break all strong ionic bonds.
-When solid, ions are held in place so solid compounds can’t conduct electricity.
-Can conduct electricity when melted.
-Some dissolve in water, making ions free to move and conduct electricity.
What are covalent bonds?
When non metals bond together, they share pairs of electrons to make covalent bonds.
Electrostatic forces and are very strong.
Atoms only share electrons in outer shells.
Atoms get one extra shared electron for each covalent bond that they form.
Each atom usually makes enough covalent bonds to fill up its outer shell. This makes them very stable.
What three ways can show covalent bonds?
Dot and cross diagrams. (electrons shared are in overlap of circles)
displayed formulas show single and double covalent bonds e.g H-N-H
3D models.
Properties of simple molecular substances in covalent bonds.
Atoms within molecules are held together by very strong covalent bonds, (e.g dot and cross diagrams) but forces of attractions between molecules are very weak.
To melt or boil a simple molecular component, you only have to break weak intermolecular forces and not covalent bonds.
So melting and boiling point is low.
Most molecular substances are gases or liquids in low temperatures.
As molecules get bigger, intermolecular forces get stronger.
Don’t conduct electricity as not charged.
Polymer properties.
Large or small molecules?
Lots of small units are joined together to form a long molecule.
Instead of drawing out a whole polymer, you can draw a small part of it called repeating unit.
To find molecular formula of a polymer, write down molecular formula of the repeating unit, put brackets around it and then an ‘n’ outside,
Strong intermolecular forces but weaker than ionic or covalent bonds, so lower bp and mp.
Examples of giant covalent structures
Diamond
Graphite
Silica
Properties of giant covalent structures
All atoms bonded by strong covalent bonds.
All have high melting and boiling points,
don’t contain charged particles, so don’t conduct electricity.
In diamond, each carbon atoms form how many covalent bonds?
Four, making diamonds really hard and covalent bonds really hard to break - high melting point.
Diamonds don’t conduct electricity as no free electrons.
In graphite, how are carbon atoms organized?
Properties of graphite.
Arranged in layers, all in hexagons (rings of six carbon atoms)
No covalent bonds between layers, so the layers can move over eachother, making graphite soft and slippery.
Lots of energy is needed to break covalent bonds, so graphite has a high melting point.
Each carbon atom has one free electron, so graphite conducts electricity and thermal energy,
What is graphene?
One layer of carbon atoms joined together in hexagons (one layer of graphite)
Covalent bonds make it very strong, also very light.
Can be added to other materials to make composites, graphene makes materials stronger but not heavier.
Conducts electricity so could be used in electronics.
What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls,
Carbon atoms mainly arranged in hexagons.
Can also form rings of five carbon atoms or rings of seven carbon atoms.
Can be used to deliver drugs into body? and great catalysts.
What is metallic bonding?
Metals are giant structures of atoms. (Lots and lots of metal atoms connected)
Electrons in the outer fell of the metal atoms are free to move around.
There are strong forces of electrostatic attraction between the positive metal ions and the charged electrons.
These forces of attraction are known as metallic bonds and hold atoms together in a regular pattern.
How does bonding in metals affect their properties?
Metallic bonds are very strong? so alot of energy is needed to break them.
This means that most substances with metallic bonds have very high melting points and usually solid at room temperature.
The delocised electrons in the metal are free to move.
These electrons can carry electrical charge and thermal energy through whole structure.
this means they’re good conductors of electricity and heat.
The layers of atoms in a metal can slide over eachother, because of this metals can be bent or formed into different shaped.
How is metallic bonding found in alloys?
Most of metal we use is alloys which is a mixture of two or more metals or a metal and another element.
Mixing another element with a pure metal causes the layers of metal atoms to lose their shapes as they have different sized atoms, making it more difficult to slide over eachother.
This makes alloys hardest so more useful than pure metal.
