Bonds, Structure & Properties of Matter Flashcards
What are the 3 types of bonding?
Ionic, Covalent and Metallic
What are ionic bonds?
Reaction between a METAL and a NON-METAL by transferring electrons. The atoms are oppositely charged particles, known as ions, in which electron transfer occurs. The opposite charges attract through ELECTROSTATIC FORCES
What are electrostatic forces?
Strong forces of attraction between particles with OPPOSITE CHARGES, and such forces are involved in IONIC BONDING. Form the basis of ionic bonding
What are covalent bonds?
Where NON-METAL atoms SHARE pairs of electrons between each other. They are very strong.
What are metallic bonds?
The sharing of many detached electrons between many positive ions, where the electrons act as ‘glue’ giving the substance a definite structure.
Very strong and are the result of the attraction between the positive metal ions and the negative delocalised electrons within the metal lattice structure
How can we represent ionic bonds?
Ionic bonds can be represented using DOT AND CROSS DIAGRAMS
What is an ionic lattice?
Formed by ionic compounds that consist of a regular arrangement of alternating positive and negative ions in which the ions are packed tightly together. Strong electrostatic forces of attraction hold the oppositely charged ions together
Boiling and melting points of ionic lattices?
Very high because of so many electrostatic forces existing in a lattice, requiring lots of energy to break these forces to change the state of the substance
What are Intermolecular Forces?
The weak attractive forces acting between molecules. These forces are much weaker than covalent bonds
Can covalently bonded molecules conduct electricity?
No, because there are no free moving electrons
I am required to be bale to draw dot and cross diagrams to represent covalent structures
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What are some examples of covalent structures?
Simple covalent molecules, Polymers and giant covalent structures
What are some models to represent covalent structures?
Dot and Cross diagrams, Ball and stick models, displayed formulas, etc
What are metal structures?
Giant structures of atoms arranged in a regular pattern, where the electrons in the outer shell of metal atoms are lost, and individual metal atoms are held together by strong metallic bonds forming a lattice structure. Within the metal lattice, the atoms lose their valence electrons and become positively charged metal ions. There is now a sea of delocalised electrons.
What occurs at the melting point?
Melting and freezing
What occurs at the boiling point?
Boiling and condensing
What are the characteristics of a solid?
There is a regular arrangements of fixed particles which vibrate in this fixed position, and are packed very close to each other
What are the characteristics of a gas?
Randomly arranged particles moving quickly in all directions and are far apart
What are the characteristics of a liquid?
Randomly arranged and move around each other whilst being close to each other
What does the amount of energy needed to change the state of a substance depend on?
The strength of the forces between the particles (intermolecular forces)
The stronger the forces of attraction, the more energy is required to overcome them of a change of state to occur
Therefore the stronger the forces between the particles the higher the melting point and boiling point of the substance
Melting
Solid to liquid
Boiling
Liquid to gas
Freezing
Liquid to solid
Evaporation
Liquid to gas
Condenstation
Gas to liquid
Sublimation
Solid to gas
What are state symbols?
Symbols written after each formula in chemical equations to show which physical state each substance is in
Solid (s)
Liquid (l)
Gas (g)
Aqueous (aq)
What does aqueous mean in state symbols?
Aqueous means the substance is DISSOLVED IN WATER, (solution)
Properties of ionic compounds
- Made of charged particles called ions which form a giant lattice structure
- High melting and boiling points due to the presence of strong ELECTROSTATIC FORCES acting between the oppositely charged ions. These forces act in all directions and a lot of energy is required to overcome them
- Solid at room temperature and are Non-Volatile (do not vaporise easily)
- Usually water soluble
Are ionic compounds good at conducting electricity?
In a solid form, no, because there are no freely moving electrons or ions, however in a molten or solution state they have ions that can move and carry charge, so can conduct electricity.
Properties of small molecules
- Compounds made up of molecules that contain just a few atoms COVALENTLY BONDED
- Low melting and boiling points
- Most covalent compounds are insoluble in water
- As the molecules increase in size, the melting and boiling points tend to increase
- Poor conductors of electricity, because there are no free moving ions or electrons to carry the charge
Why do small molecules have low melting / boiling points?
There are only WEAK INTERMOLECULAR FORCES acting between the molecules, which is why they are often liquids or gases at room temperature
What are polymers?
Large molecules of high relative molecular mass, made by linking large numbers of smaller molecules called MONOMERS
What is a monomer?
A REPEATING UNIT, and connected to the adjacent units via strong covalent bonds
What are giant covalent structures?
Structures that have huge numbers of non-metal atoms bonded to other non-metal atoms via STRONG COVALENT BONDS
Melting / boiling points, electrical conductivity, appearance and special characteristics of DIAMOND
Melting / Boiling point - Very High
Electrical Conductivity - Non-Conductor
Appearance - Transparent crystals
Special Characteristics - Hardest known naturally occurring substance
Melting / boiling points, electrical conductivity, appearance and special characteristics of GRAPHITE
Melting / Boiling point - Very high
Electrical conductivity - Good
Appearance - Grey / Black solid
Special Characteristics - Soft and slippery
Melting / boiling points, electrical conductivity, appearance and special characteristics of GRAPHENE
Melting / Boiling point - Very High
Electrical Conductivity - Very good
Appearance - Transparent sheets
Special Characteristics - Very strong and flexible ; 100 times stronger than steel
Melting / boiling points, electrical conductivity, appearance and special characteristics of BUCKMINSTER FULLERENE
Melting and boiling point - Low
Electrical Conductivity - Semi-conductor
Appearance - Yellow Solid
Special Characteristics - Very light and strong
Why are metals a good conductor of heat and electricity?
There is a sea of delocalised electrons which can move and carry a charge throughout the metal lattice structure, allowing electrons to flow so electricity is conducted well, eg. Copper
Similarly, they are good conductors of heat, where the delocalised electrons can move and carry thermal energy throughout the lattice
Properties of metals -
- Often shiny
- Malleable
- Good conductors of heat and electricity
- Usually insoluble in water although some can react with it
- Usually high melting and boiling points
What are Alloys?
Mixtures of metals where the metals are mixed together physically but are NOT CHEMICALLY COMBINED. They are often made by metals mixed with carbon. The addition of atoms of different sizes DISTORTS the layers of the regular arrangements, making it harder for the layers to slide over each other, thus much harder than the pure metal and less malleable
Properties of Alloys -
Sometimes very different to the metal they contain.
- Greater strength
- Less malleability
- Greater hardness
- Greater resistance to corrosion or extreme temperatures
What is Brass?
An alloy containing 70% copper and 30% zinc
What is an allotrope?
Different atomic or molecular arrangements of the same element in the same physical state
What is diamond?
Diamond is an ALLOTROPE of CARBON. Each carbon atom bonds with four other carbons, forming a TETRAHEDRON. All of the covalent bonds are identical, very strong and there are no intermolecular forces.
Properties of Diamond
Does not conduct electricity, has a very high melting point, very hard.
Uses of Diamond
Jewellery, coating blades in CUTTING TOOLS, heavy-duty DRILLING, etc
What is graphite?
An allotrope of carbon, where each carbon atom is bonded to three others, forming layers of HEXAGONS, leaving one free electron per carbon atom.
Uses of graphite
Pencils, Industrial lubricant in engines and locks, used to make inert electrodes, etc
What is graphene?
Consists of a single layer of graphite, and is essentially a 2D molecule since it is only 1 atom thick. It has very unusual properties making it useful in fabricating COMPOSITE materials and in ELECTRONICS
Properties of graphene
- Extremely strong and amazingly light
- Conducts heat and electricity
- Transparent
- Flexible
Why is graphene so strong?
Unbroken pattern and strong covalent bonds between carbon atoms
Why is graphene so conductive?
Free moving electrons allowing it to conduct electricity AND heat
Why is graphene so flexible?
Strong bonds between graphene’s carbon atoms are very flexible, so it can be twisted, pulled and curved to a certain extent without breaking, so it is bendable and STRETCHABLE too
Uses of graphene
- Electronics
- Sensors
- Computer screens
- Biomedical uses
What are fullerenes?
Fullerenes are a group of carbon allotropes which consist of molecules that form hollow tubes or spheres
Some uses of fullerenes
- Drug delivery systems
- Trapping catalyst molecules
- Excellent lubricants in industrial processes
What is tensile strength?
The ability of a material to resist a force that tends to pull it apart
What are nanotubes?
A type of fullerene which is created by graphene being rolled into a cylinder. It contains high tensile strength and is very resistant to breaking or stretching. Can conduct electricity.
What are some uses of Nanotubes?
- Useful in composites
- Electronics
- Nanotechnology
What are composites
A composite material consists of two or more materials with different properties . They are combined to produce a material with improved properties. Most composite materials have two components: The reinforcement, and the matrix, which binds the reinforcement together.
What are nanoparticles useful for?
Very usefully industrially in catalysis due to their high surface area to volume ratios
Advantages and Disadvantages of Nano-Particles
Adv.
- Widespread uses and applications that can provide an immense advance in materials and technology
Disadv.
- In its early stages, so there are lots of unknown factors and potential risks
- Lack of understanding about how they affect our health
- A small amount of toxicity in a particular nanoparticle would be multiplied due to the high SA / V ratio
