chemistry - topic one - key concepts

• covalent bond 


  A chemical bond formed when electrons are shared between two atoms
• ionic bond definition


  a strong electrostatic. force of attraction between these oppositely charged ions
• What are the state symbols?

  (s), (l), (g), (aq)
• Describe the history of the atom

  - Dalton described atoms as solid spheres, with different spheres making up different elements

  - JJ Thompson - plum pudding model

  - Rutherford - nuclear model after gold foil experiments

  - Bohr model has electrons in shells
• What is the charge of a proton?

  +1
• what is the charge of an electron?

  negative 1
• what is the charge of a neutron?

  0
• Which is the mass number, which if the atomic number?

  mass = protons and neutrons, atomic = just protons, so mass is always the bigger number
• What is an isotope?

  Atoms of the same element that have different numbers of neutrons
• What is relative atomic mass?

  The average mass of an atom of an element compared to one twelfth of the mass of an atom of carbon 12.
• How can you calculate Ar from isotopic abundance? (Average mass of an element's atom)

  - multiply each each RAM by abundance

  - add up results

  - divide by sum of the abundancesSee an expert-written answer!We have an expert-written solution to this problem!
• How was Dmitri Mendeleev's periodic table arranged?

  Into order of atomic mass, so that elements with similar properties would be in columns/ groups.

  This enabled him to predict the properties of undiscovered elements
• What mistakes did Mendelev make in his periodic table?


  He didn't have the masses of all elements correct, due to the prescence of isotopes, meaning that they appeared to be in the wrong columns, so he moved them.
• Which groups are most likely to form ions, and why?

  1,2,6,7 because they only have to lose/ gain one or two electrons
• What is an ion?

  A charged atom due to the loss or gain of electrons
• What are the properties of an ionic compound?

  high mpt and bpt due to strong ionic bonds which need lots of energy to be broken

  can only conduct energy when molten so that the ions can be free to carry the charge
• What types of element are ionic bonds between?

  metal and non-metal
• What are ionic bonds?

  transfer of electrons - non metal gains electrons, metal loses electrons
• What are covalent bonds?

  a chemical bond that involves the sharing of electron pairs between atoms
• What types of element form covalent bonds?

  non-metals
• what is a simple molecular structure?

  Small grouped atoms strongly held together by covalent bonding with weak intermolecular forces between molecules.
• What are the properties of simple molecular structures?

  - low melting point because weak intermolecular bonds don't require a lot of energy to break

  - cannot conduct electricity because the elctrons are not free to move so cannot carry the charge
• What are the properties of giant covalent structures?

  - high mpt and bpt due to the covalent bonds needing lots of energy to break

  - aren't soluble in water

  - don't comduct electricity because they don't contain a lot of charged particles.
• What is the structure of diamond?

  - it is made up from a nework of carbon atoms which each form 4 covalent bonds
• what is the structure of graphite?

  Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron.
• What are the properties of diamond?

  It is very hard due to its rigid lattice structure, does not conduct electricity, and has a high melting point
• What are the properties of graphene?

  Graphene has a high melting point, is strong and can conduct electricity, it is also soft and slippery (due to a lack of covalent bonds between layers), so makes an ideal lubricting material.

  It can conduct electricity because only three out of the 4 outer carbon electrons are used in bonds, so there is one delocalised one which can carry the charge
• What is the structure of graphene?

  It is one layer of graphite - carbon atoms arranged in hexagons. It is a type of fullerene.

  The sheet is only one atom thik, making it a 2D structure
• What is a fullerene?

  Substance made of carbon atoms arranged in a cage. They are mainly made from hexagons, but can also contain heptagons and pentagons.
• What is C60 fullerene?

  It is buckminsterfullerene. It forms a hollow sphere made from 20 hexagons and 12 pentagons. It is a stable molecule and forms soft brownish-black crystals
• What are fullerene nanotubes and their uses?

  They are tiny cylinders of graphene which conduct electricity. They have high tensile strength, so can be used to strengthen materials without adding too much weight. For example, they are used in sports equipment which needs to be both strong, and lightweight, like a tennis racket.
• What is the structure of a giant metallic structure?


  layers of positive metal ions, with delocalised electrons in between. The attraction between the metal ions and negative electrons is what bonds the structure together.
• What are properties of metals?

  luster, malleability, ductility, and conductivity
• What are properties of non-metals?

  Lack luster, brittle, poor heat conductors, poor electricity conductors