AQA GCSE Chemistry - Atomic structure

• group 7 and hydrogen

  hydrogen halide
• group 7 + non-metal

  Halogens + non-metal -> covalent compound
• Group 7 + metals

  Halogens + metal -> salt

  eg. sodium + chlorine -> sodium chloride
• group 7 trends

  The melting and boiling point increases as the group goes down because the halogen molecules get bigger. This means that the intermolecular forces are stronger and need more energy to break.

  - The reactivity decreases as you go down group

  - further down group higher mass
• What is group 7 structure

  Simple molecules. 2 halogen atoms with single covalent bond
• What are group 7 elements

  Halogens
• Alkaline metal + chlorine


  Alkaline metal + chlorine -> metal chloride

  This is a white solid at room temperature which dissolves in water into a colourless solution
• Alkaline metal + oxygen


  Alkaline metal + oxide -> metal oxide

  The metal oxide is a white solid which covers the surface of the metal oxide.
• Alkaline metal and water

  Alkaline metal + water -> metal hydroxide + hydrogen

  Metal hydroxide dissolves in water to create an alkaline solution
• Group 1 trends

  reactivity increases down group because molecules get bigger which means the electron has less attraction to the nucleus. The melting point decreases going down group because the atom gets larger making the intermolecular forces weaker and less energy to break
• Group 1 properties

  low density. low melting point. extremely soft.
• Group 1 are

  Alkali metals
• Group 0 trends

  The boiling point gets higher as you go down the group because the molecules get bigger which make the intermolecular forces stronger which need more energy tom break.
• Group 0 properties


  very unreactive because of full outer-shell of electrons.
• Group 0 are


  Noble gases
• Atomic number table


  The table was then organised in atomic number instead of atomic mass
• Mendeleev's periodic table

  Mendeleev arranged the elements in his periodic table in order of increasing atomic mass. However he also took into account the chemical and physical properties of elements. He created 8 groups which had similar properties. This left gaps which he predicted the properties of using trends in his periodic table which turned out to be accurate.
• Newton's periodic table

  Newton placed the elements based on atomic mass. He noticed the element 8 after has similar properties. This failed soon after which made newton's periodic table rejected by other scientists
• 3 stages of periodic table development.

  Newton, Mendeleev, atomic number
• Electron configuration in the periodic table


  The group determines the amount of electrons in the elements outer shell whilst the period determines amount of electron shells.
• Electron configuration


  Electron shells/ energy levels. Electrons occupy the lowest available energy level. 2,8,8,8,8 etc.
• How does the ions show the electrons lost or gained

  If the electrons are lost it is a positive ion so will have a + symbol next to the chemical symbol. Then it will have the number of the electrons lost next to the + symbol. Vice versa for negative electrons.
• non-metal ions

  non-metals gain electrons to become negative ions.
• metal ions

  metal atom lose electrons which they give to non-metals to create positive ions
• What are ions

  Ions are atoms which have lost or gained electrons.
• relative atomic mass calculation

  sum ( isotope abundance x isotope mass number ) / sum ( isotope abundance)
• `Whats the relative atomic mass

  The relative atomic mass is the average mass of the elements isotopes.
• where is the mass number on the isotope

  the isotope mass number is on a dash next to the chemical symbol eg. He-3 = mass 3
• Whats isotope abundance

  Isotope abundance is how common that isotope is - what percentage of all isotopes are that one.
• What are isotopes

  Isotopes of an element have the same number of protons but a different number of neutrons. They have the same atomic number but a different proton number
• What does the nuclear symbol show.

  The nuclear symbol shows the chemical symbol, the atomic ( proton) number and the mass number. The nuclear symbols are found in the periodic table.
• Subatomic ideas about the atoms

  protons and neutrons were discovered in the nucleus not just a positive charge.
• Bohr's idea on atoms

  Bohr believed that electrons must be in fixed electron shell because the electrons would otherwise naturally gravitate and spiral towards the centre of the nucleus.
• Rutherford's idea about atoms

  Rutherford conducted the gold foil experiment also known as the alpha scattering experiment. He sent a beam of alpha particles at a thin strip of gold foil. Some particles were rebounded proving their was a nucleus in the centre of the atom. It looked like the plum pudding model with a positive nucleus in the middle.
• Thomson's idea about atoms

  Thomson created the plum pudding model after the discovery of electrons. It was a positive ball of mass with negative embedded electrons
• Dalton's ideas about atoms


  He believed atoms were solid positive mass which could not be created or divided.
• What are the 5 stages of the scientific model of the atom

  Dalton, Thomson, Rutherford, Bohr and subatomic particles.
• What are the 3 particle types

  molecules, ions, atoms
• What is the edge of the solvent called

  Solvent front
• Rf value calculation


  Distance travelled by soluble solid/ distance travelled by solvent