Periodicity 🗣️

• How is the periodic table now arranged?

  Left to right - increasing atomic number

  vertical columns- groups have the same number of outer shell electrons and therefore similar properties

  horizontal rows- periods and shows the number of shells
• what is first ionisation energy?

  the energy required to remove one mol of electrons from one mole of atoms to form one mol of 1+ions at a gaseous state
• how does atomic radius affect ionisation energy?

  further the outermost shell= larger the atomic radius= less nuclear attraction between outermost electron and nucleus= easier to remove= lower ionisation energy
• how does nuclear charge after first ionisation energy?

  more protons= greater attraction to outer electrons
• what is shielding and how does it affect first ionisation energy?

  when electrons in the inner shells repel the outer shell electrons

  more shielding= less attraction
• in terms of successive ionisation energy what would be the definition of second ionisation energy?

  the energy required to remove one mole of electrons from one mol of atoms to form one mole of 2+ions in a gaseous state
• Explain the general trend of first ionisation energy Down a group?

  • atomic radius increases because number of shells increase = energy decreases
  • more shielding as more electrons fill that shell= energy decreases
  • nuclear attraction on outermost electron decreases
• what is the general trend of first ionisation energy across a period?

  • nuclear charge increases as the number of protons increase, this also makes the radius decrease slightly
  • the all have the same number of shells so same shielding
  • nuclear attraction increases
• What are the two exceptions in trends across period two?

  • Beryllium and boron- boron’s outermost electron is in the 2p subshell. beryllium's is in 2s —> 2p sub shell require less energy to remove
  • nitrogen and oxygen- both outermost electron are in 2p sub shells but oxygen has one set of paired electrons in the orbital —> like charges repel so the outermost electron is more easy to remove
• What properties do metals have?

  Strong metallic bonds, high electrical conductivity, high melting and boiling point
• why and when can metals conduct electricity?

  in solid and liquid states as the delocalised electrons can move and carry charge
• What is metallic bonding?

  strong electrostatic attraction between cations (positive ions) and delocalised electrons

  • the cations are fixed in position and the electrons are mobile and can move through the structure
• Do metals dissolve?

  No, as any interaction would lead to a reaction
• What is a covalent bond?

  the electrostatic bond between two nuclei and the outermost electron that they share
• what is the structure and bonding of usual non metallic elements?

  simple molecular lattice- bonded by weak London forces so have low melting and boiling points
• Which elements form giant covalent structures?

  Boron, carbon and silicon
• how many bonds does carbon and silicon form why and what does this allow?

  they form 4 bonds because they have four electrons in the outer shell and need four more, therefore tetrahedral structure= bond angle of 109.5
• what are the properties of giant covalent lattices?

  • high melting and boiling points because of covalent bond
  • strong bonds also make them insoluble
  • carbon as diamond and silicon cant conduct electricity as all 4 outer shells are involved in bonding
  • carbon as graphene and graphite can conduct electricity
• what are the properties of graphite and graphene?

  Hexagonal structure= bond angle of 120

  only three of the four electrons available are covalently bonded, one electron donated to pool of delocalised electrons

  • graphene- single layer of graphite and thinnest strongest material ever made
  • graphite- parallel layers of graphene, layers are bonded by London forces
• what is the trends in melting point across period 2 and 3?

  Period 2: lithium beryllium= giant metallic/ boron carbon= giant covalent/ simple molecular Period 3: sodium magnesium aluminium= giant metallic/ silicon= giant covalent/ simple molecular