Structure And Bonding Flashcards
What are the three types of bonding
Covalent bonding
Ionic bonding
Metallic bonding
What is ionic bonding
Involves an attraction between oppositely charged ions. Found in compounds
Metal atoms lose electrons to become positively charged ions
Non metals gain electrons to become negatively charged ions
What is covalent bonding
Formed when 2 non metal atoms share pairs of electrons. Strong because the shared electrons are attracted to the nucleus of both atoms
What is metallic bonding
Involves an attraction between positively charged ions and negatively charged delocalised electrons
What are examples of covalent molecules
Small molecules- eg water
Large molecules- eg polyester
Giant covalent structures- eg diamond
What are the advantages and limitations of dot and cross diagrams
Shows the pairs of outer electrons and which atoms theyve come from
Doesn’t show how the atoms are arranged in space
What are the advantages and limitations of a ball and stick diagram
Fails at indicating movement of electrons
Also 2D
What are the properties of solids
Particles are very close and vibrate at a fixed position
Fixed shape and volume
When heated the particles vibrate with a greater amplitude
What are the properties of liquids
Particles are close together but they move and flow randomly
Have fixed volume but can change shape
When heated the average speed of particles increases
What are the properties of gases
Particles are far apart and move randomly in all directions
Gases change shape and volume
Negligible forces
What are the disadvantages to the “simple sphere” model
Forces between the particles aren’t shown as a result it’s impossible to know how strong these forces are and how much energy is needed
Portrays particles in a spherical way but they arnt
Portrays particles as solid when they arnt
What happens when particles gain or lose energy
Because of heating/cooling-they overcome or submit to the forces of other particles which causes them to change shape
What are the 4 types of state changes
Melting- (s-l)
Condensing- (g-l)
Boiling-(l-g)
Freezing-(l-s)
What happens with stronger forces
Stronger forces between particles means more energy is required to overcome those forces. They have higher melting and boiling points
What happens with weaker forces
Weaker forces between particles means less energy is required to overcome those forces. Have lower melting and boiling points
What does aq mean as a state symbol
Aqueous solutions (substances dissolved in water)
What are the properties of ionic compounds
High melting and boiling points- lots of energy is needed to overcome the electrostatic forces between the ions and electrons in the lattices
Because if this they have high melting and boiling points
Properties of ionic compounds (2)
Cannot conduct electricity when solid-when solid the ions in the lattice are fixed in place . TMT changes cannot flow so electricity can’t be conducted
Can conduct electricity when liquid-when dissolved in liquid the ions in the lattice are free to move because of this charge can flow and electricity can be conducted
Why do small covalent molecules have low melting and boiling points
. Intermolecular forces are much weaker than the strong covalent bonds in molecules. When small molecular substances melt or boil, it is these weak intermolecular forces that are overcome. The covalent bonds are not broken. Relatively little energy is needed to overcome the intermolecular forces, so small molecular substances have low melting and boiling points.
Why do bigger molecules have higher melting and boiling points
Because the smaller the molecule, the weaker the intermolecular forces.
Why don’t small or big covalent molecules conduct electricity
They cannot conduct electricity because they do no have an overral electric charge
Why are polymers solid at room temperature
They have very large molecules. Atoms in the polymer molecules are linked to other atoms by strong covalent bonds. Intermolecular forces between polymer molecules are relatively strong and require a lot of energy to overcome them
What are the properties of Giant Covalent structures
No specific formula-because the structure can be any size
Very high melting points- because of strong covalent bonds
1 large molecule-Giant covalent structures exist as 1 large molecule. Means there are no intermolecular forces
What are examples of giant covalent structures
Diamond
Graphite
Graphene
Fullerenes
What are the properties of pure metals
High melting and boiling points-strong electrostatic forces between metal ions and delocalised electrons and giant structures of atoms
Soft and malleable-because the ions are arranged in layers they Slide Over eachother and be bent and shaped. This means they are too soft and should be mixed with other metals to make alloys which are harder
What are metals as conductors like
Good conductors of electricity because the delocalised electrons in the metal carry electrical charge through it
Good conductors of heat because energy is transferred by the delocalised electrons
What are alloys
A mixture is 2+ elements where at least one is a metal
Why are alloys harder than metals
The different sized atoms distort the layer making them harder to Slide Over eachother. However the ions in metals are arranged in layers so they Slide Over eachother easily
What are the properties of diamond
Doesn’t conduct electricity-because there are no delocalised electrons in its structure (bonded to 4 carbon atoms)
High melting point and is very hard- has lots of strong covalent bonds making it hard and having a high melting point
What are the properties of graphite
Soft-carbon atoms form layers of hexagonal rings with each layer held together by weak intermolecular forces. Layers Slide Over and have no covalent bonds between the layers so it’s very soft
Conducts electricity-it is bonded to 3 carbon atoms which means that there is 1 delocalised electron which moves freely to carry the charge
What are the properties of Graphene
Conducts electricity-single layer of graphite so it also conducts electricity
Light but strong-Graphene is 1 layer thick. Makes it light however the atoms within the layers are tightly bonded and elastic because the planes of atoms can flex relatively easily without the atoms breaking
Useful in electronics and composites
What was the first fullerene to be discovered and properties
Buckminster fullerene
Molecules of carbon atoms with hollow shapes
Based on hexagonal rings of carbon atoms but they may also contain rings with 5 or 7 carbon atoms
What is the formula of buckminster fullerene
C60
What are the common uses of these fullerenes
Catalysts
Lubricants
Delivering drugs into the body
What are the properties of carbon nanotubes
Cylindercal fullerenes with very high length to diameter ratios
What are the uses of carbon nanotubes
Nanotechnology, electronics and materials
What is the structure of sodium chloride
Na+ and Cl-
What are the molecules of hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane
H2, HCl, O2, Cl2, NH3 and CH4
How does particle theory help to explain melting boiling freezing and condensing
The amount of energy needed to change state from a solid to liquid and from liquid to gas depends on the strength of the forces between particles
The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting and boiling point
