Periodicity

• What is periodicity

  Trends in the physical and chemical properties within groups and periods in the periodic table
• Trends

  Elements that are in the same group have the same number of outer electrons.

  As it is the electrons that are involved in a chemical reaction, elements in the same group will have similar properties and will take part in similar reactions.
• Blocks

  Groups 1 and 2 make up the S block
• Blocks

  The D block consists of the transition metals, which have their outer most electrons in the D sub-shell
• Blocks

  Groups 3 to 8 make up the P block and these elements have their outermost electron in the P sub-shell.
• Blocks

  The F block consists of the lanthanides and actinides
• Ionisation energies


  Ionisation energy is the required energy to remove one mole of electrons from one mole of gaseous atoms of an element.

  If it is the first electron being removed it is called the first ionisation energy, the second electron is called the second ionisation energy and so on.
• Ionisation energies

  The higher the ionisation energy the harder it is to remove an electron
• Factors of ionisation energies

  Nuclear charge - the higher the nuclear charge the greater the force of attraction between the positive nucleus’s and the negative electrons.

  Atomic radius - the greater the distance between the nucleus and outer electrons the weaker the attraction between the nucleus and outer electrons making them easier to remove.

  Electron shielding - the more electrons located between the outer electrons and the nucleus the more they shield the attraction between the outer electrons and the nucleus making the electrons easier to remove.
• Trends in ionisation energies

  As you go across a period ionisation energy increases there is an increasing nuclear charge and so a greater force of attraction between the nucleus and electrons.
• Trends in ionisation energies


  As you go down a group there is a decrease in ionisation energy as although there is an increased nuclear charge there is also a larger atomic radius and more electron shielding which weakens the attraction between the nucleus and outer electrons making them easier to remove.
• Trends

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• Exceptions to trends in ionisation energies across a period.

  There’s a small drop in ionisation energy between groups 2 and 3. The outer electron is occupying a P orbital which is slightly further from the nucleus than an S orbital making them have a slightly larger atomic radius and more electron shielding. This overrides the effect from the additional proton.
• Exceptions to the trends in ionisation energy across a period

  There is a dip in ionisation energy between groups 5 and 6. In group 5 the outer electrons are in their own orbitals. In group 6 electrons have to begin pairing. As electrons are negatively charged the electron pairs repel each other. the repulsion between electrons make the outer paired electron easier to remove.
• Periodic trends in structure and boiling point.

  Metallic bonding is the type of bonding in metals. It is electrostatic attraction between the positive metal ions and the delocalised electrons.
• Advantages of metallic bonding

  High melting and boiling points - strong metallic bonding.

  Good conductors of heat and electricity - the delocalised electrons are able to move and carry a current.

  Malleability - the layers of metal ions are able to slide over each othe.
• Giant covalent molecules

  Diamond is a giant covalent molecule. It is made up of carbon atoms bonded to 4 other carbon atoms giving it a stable structure. The atoms are joined by covalent bonds making diamond very hard and giving it a high melting and boiling point. It is not able to conduct as it does not have any charged particles that can move.

  Graphite is a giant covalent structure made up of carbon atoms bonded to only 3 other carbon atoms in a planar hexagonal arrangement meaning that one of the carbon atoms electrons become delocalised and can move throughout the structure.
• Trends in melting and boiling points

  Metals have high melting and boiling points.

  Giant covalent lattice structures the melting and boiling points are high due to strong covalent bonding.

  Simple covalent structures have low melting and boiling points as the covalent bonds stay intact and it is the intermolecular forces that break when changing state.

  the noble gases have the lowest melting and boiling points as they have weak intermolecular forces as they exist as single atoms