1 / 15

The Trends in Elements in 1-20

The Trends in Elements in 1-20. Atomic Size. Ionisation Energies. Covalent Radius. Element. Atomic Number. Atomic Size. Hydrogen. 1. 37. Helium. 2. --. Lithium. 3. 134. Beryllium. 4. 129. Boron. 5. 90. Carbon. 6. 77. Nitrogen. 7. 75. Oxygen. 8. 73. Fluorine. 9.

nichole-osborn
Download Presentation

The Trends in Elements in 1-20

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Trends in Elements in 1-20 Atomic Size Ionisation Energies

  2. Covalent Radius Element Atomic Number Atomic Size Hydrogen 1 37 Helium 2 -- Lithium 3 134 Beryllium 4 129 Boron 5 90 Carbon 6 77 Nitrogen 7 75 Oxygen 8 73 Fluorine 9 71

  3. Atomic Number versus Atomic Size A t o m i c S i z e K Na Li Cl F Atomic Number

  4. The graph shows that 1. As we go across a period the atomic size decreases 2. As we go down a group the atomic size increases We can explain the pattern or trend shown in this graph by considering 2 areas 1. Number of Electron Shells (energy levels) (The electron arrangement) Always consider this first 2. The nuclear charge of the atom This is given by the atomic number

  5. Nuclear Charge Electron Arrangement Atomic Size (Covalent radius) 1 + 1 Hydrogen 37 2 + 2 Helium -- 3 + 2 , 1 Lithium 134 4 + 2 , 2 Beryllium 129 5 + 2 , 3 Boron 90 6 + 2 , 4 Carbon 77 7 + 2 , 5 Nitrogen 75 8 + 2 , 6 Oxygen 73 9 + 2 , 7 Fluorine 71 10 + 2 , 8 Neon --

  6. Hydrogen 1 + 1 37 Lithium 3 + 2 , 1 134 Beryllium 4 + 2 , 2 129 Boron 5 + 2 , 3 90 Explanation of properties An increase in nuclear charge pulls the electrons closer to the nucleus giving a smaller atomic size An increase in the number of electron shells means an increase in the atomic size

  7. Lithium 3 + 2 ,1 134 Sodium 11 + 2 ,8,1 154 Potassium 19 + 2 ,8,8,1 196 Group 1 elements As we go down the group the number of electron shells increases. The outer electrons are further from the nucleus, This gives a larger atom The extra shell of electrons also shields the outer electrons from the attraction of the positive nucleus This gives a larger atomic size

  8. If you are asked to compare the size of ions remember that the electron arrangement of an ion is not the same as the atom Why is the ionic radius of P3- so much greater than that of Si4+ P 15+ 2)8)5 P3- 15+ 2)8)8 but The negative ion has 3 more electrons, giving a full shell Si 14+ 2)8)4 Si4+14+ 2)8 but The positive ion has 4 less electrons, one less shell The difference in size is caused by the extra shell of the negative ion

  9. E (g) E+ (g) + e- Ionisation Energies Ionisation energies can be explained by considering the same points 1. Number of Electron Shells (energy levels) (List the electron arrangement ; This will change for the ions) 2. The nuclear charge of the atom (This does not change when it becomes an ion)

  10. Element Nuclear Charge Electron Arrangement First I.E.(kJ mol-1) Lithium 3 + 2 , 1 526 4 + Beryllium 2 , 2 905 5 + Boron 2 , 3 807 6 + Carbon 2 , 4 1090 7 + Nitrogen 2 , 5 1410 The trend is : As we go across a period the first ionisation energy increases

  11. Lithium 3 + 2 , 1 526 kJ Beryllium 4 + 2 , 2 905 kJ Explanation of properties An increase in nuclear charge pulls the electrons closer to the nucleus giving a smaller atomic size The outer electrons are therefore more stongly held. This means more energy is needed to remove the outer electron

  12. Lithium 3 + 2 , 1 526 kJ Sodium 11 + 2 , 8, 1 502 kJ Explanation of properties An increase in number of shells means the outer electrons are further from the nucleus and shielded by the extra shell The outer electrons are therefore less strongly held. This means less energy is needed to remove the outer electron This means a smaller ionisation energy

  13. M+ (g) M2+ (g) + e- Second Ionisation Energies The difference in values between first and second ionisation energies can be explained by considering the same points 1. Number of Electron Shells (energy levels) 2. The nuclear charge of the atom Remember ions have different electron arrangements from their atoms

  14. Sodium Na 11 + 2 , 8, 1 502 kJ Sodium Na+ 11 + 2 , 8 4506 kJ Explanation of Second IE An decrease in number of shells means the outer electrons are closer to the nucleus and no longer shielded by the extra shell The outer electrons are therefore more strongly held. This means more energy is needed to remove the outer electron This means a larger ionisation energy

  15. Magnesium Mg 12 + 2 , 8, 2 744 kJ Magnesium Mg+ 12 + 2 , 8, 1 1460 kJ Magnesium Mg2+ 12 + 2 , 8 7750 kJ The large increase on going from second to third ionisation energy is when the last electron in the shell has been removed The outer electrons are therefore more strongly held. This means more energy is needed to remove the outer electron This means a larger ionisation energy

More Related