C3 - Structure and Bonding Flashcards
What is an alloy?
A mixture of two or more elements, at least one of which is a metal
What is a Covalent bond?
the bond between two atoms that share one or more pairs of electrons
What is covalent bonding?
the attraction between two atoms that share one or more pairs of electrons
What is a delocalised electron?
bonding electron that is no longer associated with any one particular atom
What is a dot and cross diagram?
a drawing to show only the arrangement of outer shell electrons of the atoms or ions in a substance
What is a fullerene?
Carbon allotropes which exist in the form of large, hollow, spherical molecules in a cage-like strucuture. Based on hexagonal rings of carbon atoms
What are gases?
substances that have no fixed shape or volume and can be compressed easily
What is a giant covalent structure?
a huge 3D network of covalently bonded atoms
What is a giant lattice?
a huge 3D network of atoms or ions
What is a giant structure?
a huge 3D network of atoms or ions
What are intermolecular forces?
the attraction between the individual molecules in a covalently bonded substance
What is an ionic bond?
the electrostatic force of attraction between positively and negatively charged ions
What is a liquid?
substances that have a fixed volume, but they can flow and change their shape
What is nanoscience
the study of very tiny particles or structures between 1 and 100 nanometres in size
What is particle theory?
a theory that explains the properties of solids, liquids and gases based on the fact that all matter is made from tiny particles. It describes the movement of particles and the distance between them
What is a polymer?
a substance made from very large molecules made up of many repeating units
What are solids?
substances that have a fixed shape and volume that cannot be compressed. the particles cannot move, only vibrate
What is states of matter?
the forms in which matter can exist. A substance can be solid, liquid or gas
In melting and boiling the energy is transferred from ……… to the …………
In melting and boiling the energy is transferred from the surroundings to the substance
In freezing and condensing the energy is transferred from ……… to the …………
In freezing and condensing the energy is transferred from substance to the surroundings
What are the limitations of particle theory?
The particle model is limited as it assumes particles are solid spheres with no forces between them, however particles can be atoms, molecules or ions. They can vary in size. They can contain many atoms and they are not solid or spherical.
What is covalent bonding?
Covalent bonding is the electrostatic attraction between a shared pair of electrons and the nuclei of 2 atoms. (When 2 atoms share a pair of electrons)
What is Ionic bonding?
Ionic bonding is the electrostatic attraction between oppositely charged ions
What type of elements form positive ions?
metals
What type of elements form negative ions?
non-metals
What do dot and cross diagrams show?
the electron transfer during the formation of an ionic compound
What is the arrangement of ionic bonding?
a giant lattice structure
What is the conductivity of ionic bonds as a solid?
they do not conduct
What is the conductivity of ionic bonds as a liquid?
they can conduct
What is an ion?
A charged atom formed by the loss or gain of electrons
Why do atoms lose or gain electrons to form ions?
To obtain a full outer shell of electrons
What are negative ions called?
Anions
What are positive ions called?
Cations
What is the formula of Lithium?
Li¹+
What is the formula of Potassium?
K¹+
What is the formula of Silver?
Ag¹+
What is the formula of Magnesium?
Mg²+
What is the formula of Copper?
Cu²+
What is the formula of Aluminium?
Al³+
What is the formula of Chromium?
Cr³+
What is the formula of Ammonium?
NH₄¹+
What is the formula of Fluoride?
F¹-
What is the formula of Bromide?
Br¹-
What is the formula of Hydroxide?
OH¹-
What is the formula of Chloride?
Cl¹-
What is the formula of Nitrate?
NO₃¹-
What is the formula of Sulfate?
SO₄²-
What is the formula of Carbonate?
CO₃²-
What is the structure of an ionic compound?
Giant Lattice
What state are ionic compounds at room temperature?
Solid
Why do ionic compounds have a high melting point?
Lots of energy is required to break every ionic bond
In what state do ionic compounds conduct?
Liquid/aqueous solution
Why do ionic compounds only conduct as a liquid or an aqueous solution?
Ionic compounds contain charged particles but the particles are not free to move as a solid as they are fixed in a lattice, when molten these particles can move freely and can conduct
What does the formula Na₂S mean?
the ionic compound Sodium Sulphate has Sodium ions and Sulphur ions in the ratio 2:1
What is a molecule?
A substance made up of non-metal atoms joined by covalent bonds
When are covalent bonds formed?
When atoms share a pair of electrons
What are the advantages of using dot and cross models to represent molecules?
They are useful for illustrating sharing/transfer of electrons. They indicate which atoms the shared electrons have come from.
What are the disadvantages of using dot and cross models to represent molecules?
They fail to illustrate the 3d arrangement of the atoms and the electron shells. They do not indicate the relative size of atoms and subatomic particles.
What are the advantages of using 3d “stick” representation of molecules?
They are useful for illustrating the arrangements of atoms in 3d space. They are very useful for visualising the shape of the molecule
What are the disadvantages of using 2d “stick” representation of molecules?
They fail to indicate the movement of electrons. The atoms are placed far apart from each other, which in reality is not the case as the gaps between atoms are much smaller.
ions are formed when what type of elements react?
metals and non-metals
What type of elements lose electrons?
metals
What type of elements gain electrons?
non-metals
Explain what the formula Al₂O₃ tells us about aluminium oxide?
The ionic compound of Aluminium Oxide contains Aluminium ions and Oxygen ions in the ratio 2:3
Aluminium oxide has a very high melting point while carbon dioxide has a very low melting point. Explain this difference.
Aluminium oxide is ionically bonded and therefore has many strong ionic bonds between each ion. For it to melt every bond needs to be broken and therefore a lot of energy is required whereas Carbon Dioxide has simple molecular bonding and therefore has a low melting point as it has weak intermolecular forces between each molecule which do not require much energy to break.
Carbon dioxide does not conduct electricity in any state whereas aluminium oxide will conduct electricity when it is molten. explain this difference.
For a substance to conduct it needs to have mobile charged particles. Carbon dioxide is covalently bonded and therefore does not have any charged particles. That means that the carbon dioxide cannot conduct in any state. Aluminium oxide is ionically bonded which means that it does have charged particles. When it is in a solid state it does not have “mobile particles” as it is fixed in a lattice and therefore cannot conduct, however when molten it does have charged particles that are free and can therefore conduct.
Explain why ammonia has a low melting point.
Ammonia has a simple molecular structure, this means that it has weak intermolecular forces and very little force is required to break these bonds.
Explain why diamond is hard but graphite is soft.
Diamond has a giant covalent lattice and each carbon atom is bonded to 4 other carbon atoms. On the other hand, graphite is formed in layers and each carbon atom is bonded to only 3 other carbon atoms. This causes graphite to be soft as the layers of graphene can slide off of each other
Why does graphite conduct but diamond cannot?
For a substance to conduct it needs to have mobile charged particles. Diamond is covalently bonded and it does not have any delocalised electrons, this means that diamond does not have any mobile charged particles and cannot conduct. Whereas graphite is formed in layers and each carbon atom is bonded to only 3 other carbon atoms. This causes there to be an extra unbonded electron, thus forming a sea of delocalised electrons. These delocalised electrons are free to move and they are charged. This means that graphite can conduct.
What do dots/crosses represent in a dot and cross diagram?
electrons
What is the structure type of Diamond?
Giant Covalent
What is the structure type of Graphite?
Giant Covalent
What is the structure type of Buckminsterfullerene?
Simple Molecular
What is the structure type of Graphene?
Giant Covalent
What is the formula of Diamond?
C
What is the formula of Graphite?
C
What is the formula of Buckminsterfullerene?
C₆₀