C2,C3,C4 Flashcards
Sodium chloride is an ionic compound.
Describe the structure of a crystal of sodium chloride
Ionic compounds such as sodium chloride are arranged in a giant lattice structure, which is a regular repeating pattern of positive and negative ions. There are strong electrostatic forces of attraction that hold the oppositely charged ions together in the giant lattice.
Why does sodium chloride have a high melting point
Sodium chloride has a high melting point and boiling point because of the strong electrostatic attraction between its positive and negative ions. This requires more heat energy to overcome the force of attraction.
Name the force that holds ions together in an ionic bond
Electrostatic force
From a dot and cross diagram, how can you tell that the particles in a compound are held together by an ionic bond
The electrons from one atom are shown as dots, and the electrons from the other atom are shown as crosses
Choose the correct words
In an ionic compound, the particles are held together by weak/strong forces of attraction.
These forces act in all directions/in one particular direction which results in the particles bonding together to form giant lattices/small molecules.
Strong forces of attraction.
In all directions.
Giant lattices.
Which of the following is not typical for an ionic compound
High melting point
High boiling point
Conduct electricity in the solid state
Conducts electricity in the liquid state
Conduct electricity in the solid state
How does the structure of the ionic compound pottasium bromide cause it to have a high boiling point
Ionic compounds have high melting and boiling points because they have a giant structure with strong electrostatic forces between oppositely charged ions that require a lot of energy to break
How does the structure of the ionic compound pottasium bromide cause it to have a low electrical conductivity of solids
Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move
How does the structure of the ionic compound pottasium bromide cause it to have a high electrical conductivity as a liquid
Ionic compounds can conduct electricity when melted or dissolved in water. During these states, the charged particles called ions are able to move freely. In contrast, the ions are stationary when the ionic compound is in a solid crystalline state
Decribe how two atoms come together to form a single covalent bond
A covalent bond is formed when a pair of electrons is shared between non metal elements
Describe how the hydrogen atoms in a methane molecule are bonded to the carbon atom
For example, in methane (CH 4 ), carbon forms covalent bonds with four hydrogen atoms. Each bond corresponds to a pair of shared electrons (one from carbon and one from hydrogen), giving carbon the eight electrons it needs for a full outer shell.
compare the strength of the bonds of covalent, metallic and ionic.
Which is stronger?
The covalent bond is usually weaker than the metallic and the ionic bonds but much stronger than the intermolecular forces
When a simple molecular substance melts, is it the bonds between atoms or the forces between molecules that are broken?
The forces between the molecules are broken
predict with reasons whether iodine can conduct electricity in any state
There are no delocalized electrons in iodine, and no ions, so there are no charge carriers and iodine cannot conduct electricity.
Why does methane have a lower boiling point to that of butane
Butane is a larger molecule than methane meaning that the intermolecular forces between its molecules are stronger. In order for a compound to boil these intermolecular forces need to be overcome.
What are the 4 main allotropes of carbon
Diamond, buckminsterfullerene, graphite, graphene
Properties of diamond:
Structure type -
Strength -
Number of covalent bonds each Carbon atom forms -
Melting and boiling points -
Reasons for melting and boiling points -
Electrical conductivity -
Reasons for electrical conductivity -
Structure type - giant covalent
Strength - very hard and strong
Number of covalent bonds each Carbon atom forms - 4
Melting and boiling points - very high
Reasons for melting and boiling points - need to break strong covalent bonds
Electrical conductivity - insulator
Reasons for electrical conductivity - has no delocalised electrons
Properties of graphite :
Structure type -
Strength -
Number of covalent bonds each Carbon atom forms -
Melting and boiling points -
Reasons for melting and boiling points -
Electrical conductivity -
Reasons for electrical conductivity -
Structure type - giant covalent
Strength - soft and brittle
Number of covalent bonds each Carbon atom forms - 3 (1 =delocalised)
Melting and boiling points - very high
Reasons for melting and boiling points - need to break strong covalent bonds
Electrical conductivity - conductor
Reasons for electrical conductivity - has no delocalised electrons that can carry charge through structure.
Buckminsterfullerene properties :
Structure type -
Strength -
Number of covalent bonds each Carbon atom forms -
Melting and boiling points -
Reasons for melting and boiling points -
Electrical conductivity -
Reasons for electrical conductivity -
Structure type - simple molecular
Strength - soft and brittle
Number of covalent bonds each Carbon atom forms - 3 (1=delocalised)
Melting and boiling points - not so high
Reasons for melting and boiling points - need to overcome relatively weak forces between molecules ( no covalent bonds broken).
Electrical conductivity - insulator
Reasons for electrical conductivity - has delocalised electrons but they cannot move from one molecule to another.
Properties of Graphene :
Structure type -
Strength -
Number of covalent bonds each Carbon atom forms -
Melting and boiling points -
Reasons for melting and boiling points -
Electrical conductivity -
Reasons for electrical conductivity -
Structure type - giant covalent
Strength - very strong
Number of covalent bonds each Carbon atom forms - 3 (1=delocalised)
Melting and boiling points - very high
Reasons for melting and boiling points - need to break strong covalent bonds
Electrical conductivity - conductor
Reasons for electrical conductivity - has delocalised electrons that can carry charge through structure
State a use of graphene
Graphene is a strong, light and relatively inexpensive electrical conductor and will be used in solar cells and batteries
how does the bonding and structure of graphite make it suitable to make components in electrical circuits
Graphite has delocalised electrons, just like metals. These electrons are free to move between the layers in graphite, so graphite can conduct. electricity. This makes graphite useful for electrodes
Describe a metallic bond
A metallic bond is the electrostatic force of attraction between the lattice of positive ions and the delocalised outer shell electrons.
How many delocalised electrons will there be per atom in
Group 1 metal elements -
Group 2 metal elements -
Group 3 metal elements -
Group 1 =1
Group 2 =2
Group 3=3
Why are metals good conductors of electricity
because the electrons are free to move in a network of the metal atom
explain how the structure and bonding in metals means that they are able to be bent and shaped
This is because they consist of layers of ions that can slide over one another when the metal is bent, hammered or pressed. Due to the ions sliding over each other, most metals are ductile – they can be drawn/pulled into wires, making them suitable for electric cables
explain why it is usually easier to change the shape of a pure metal than an alloy
In an alloy, there are atoms of different sizes. The smaller or bigger atoms distort the layers of atoms in the pure metal. This means that a greater force is required for the layers to slide over each other. The alloy is harder and stronger than the pure metal.
Which requires more energy melting or boiling
Boiling
Out of Ionic, covalent and metallic bonds.
Which bond is the strongest?
Covalent bonds are held together by the sharing of electrons between the atoms. Metallic bonds are held together by the sharing of electrons between metal atoms. Ionic bonds are typically stronger than covalent bonds, which in turn are typically stronger than metallic bonds.
how did the discovery of isotopes explain why atomic weights do not always give the correct order of elements
Discovery of isotopes of the same element explained the order based on atomic mass was not always correct. When scientists discovered isotopes it explained why some atoms had heavier atomic masses than expected. This meant that Mendeleev was correct to not stick to arranging the periodic table according to atomic mass
Why is the table called the periodic table
It is called the periodic table because of the way the elements are arranged. You’ll notice they’re in rows and columns. The horizontal rows (which go from left to right) are called ‘periods’ and the vertical columns (going from up to down) are called ‘groups’
How can you tell what period an element is in
the number of circles in the electronic configuration of an element is represented in the periodic table as the period number that element is situated in
In a chemical reaction what is the excess and the limiting reactant
In a chemical reaction involving two reactants, it is common to use an excess of one of the
reactants to ensure that all of the other reactant is used. The reactant that is completely used up is
called the limiting reactant because it limits the amount of products.
What is the atom economy
The atom economy (atom utilisation) is a measure of the amount of starting materials that end up
as useful products. It is important for sustainable development and for economic reasons to use
reactions with high atom economy.
The percentage atom economy of a reaction is calculated using the balanced equation for the
reaction as follows:
Relative formula mass of desired product from equation × 100
Divided by
Sum of relative formula masses of all reactants from equation
