Atomic Structure and the Periodic Table

• What are the five methods through which mixtures can be separated?

  > Filtration: separate an insoluble solid suspended in a liquid

  > Crystallisation: separations of s solid dissolved in a solvent from a solvent. Does not keep the solvent

  > Simple distillation: separate liquid from a solution, keeps the liquid

  > Fractional distillation: separation of a mixture of liquids when they have diff boiling points

  > Chromatography: separate a mixture of substances dissolved in a solvent
• Describe the plum pudding model:

  Atom is a ball of positive charge with negative electrons embedded in it
• Describe the Bohr/nuclear model and how it came about:

  Suggests that electrons orbit the nucleus at specific distances (shells)

  It came about from the alpha scattering experiment
• What did the work of James Chadwick provide evidence for?

  The existence of neutrons in the nucleus
• State the relative masses and charges of the proton, neutron and electron

  Proton mass: 1

  Charge: +1

  Neutron mass: 1

  Charge: 0

  Electron mass: very small

  Charge: -1
• Why are atoms electrically neutral?

  They have the same number of electrons and protons
• What is the atomic number?

  Number of protons in the nucleus
• Atoms of the same element have the same number of which particle in the nucleus?

  Protons
• What is the mass number?

  Number of protons + neutrons
• What is an isotope?

  Atoms of the same element (same proton number)

  that have a different number of neutrons

  They have the same chemical properties as they have the same electronic structure
• What is relative atomic mass?

  The average mass value which takes the mass and abundance of isotopes of an element into account on a scale where the mass of 12C is 12
• What are ions?


  Charged particles formed when atoms lose or gain electrons
• What change in shell number is seen as one moves down a group?

  The number of shells increases
• Characteristics if Alkali (group 1) metals 


  Soft

  Very reactive

  1 electrons in valence shell

  Reactivity increases down the group

  -> they get bigger and so it is easier to lose an electrons that is further away from the nucleus
• How do group 1 elements react with water?

  They release hydrogen and form hydroxides which dissolve to from alkaline solutions

  They react vigorously with water fizzing and moving around
• Characteristics of Halogens (group 7)

  Coloured vapours

  Diatomic molecules

  Form ionic salts with metals

  Reactivity decreases down the group because it is harder to gain an electron because its outer shell is further away from the nucleus
• Characteristics of transitions metals:

  Ions with different charges

  Coloured compounds

  Catalytic properties
• Characteristics of Noble gases (group 8/0):

  Non metals

  Unreactive due to full outer shell

  All colourless gases at room temp

  Boiling point increases down the group as the atoms get heavier