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Electrons in atoms.

Electrons in atoms. As atoms are neutral the number of electrons is given by the atomic number. Electron shells. Electrons orbit the nucleus in shells . The first shell, the one nearest the nucleus , can only have two electrons. The next shell can have 8 . The third shell 18 .

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Electrons in atoms.

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  1. Electrons in atoms. As atoms are neutral the number of electrons is given by the atomic number.

  2. Electron shells • Electrons orbit the nucleus in shells. • The first shell, the one nearest the nucleus, can only have two electrons. • The next shell can have 8. • The third shell 18. • (Although it can be partially full with 8). • The lower shells must be filled first before electrons can be put into the upper shells.

  3. carbon atom X X X X atomic number X X C 2 , 4 6 so six electrons X X X X X X

  4. lithium atom X X X atomic number Li 2 , 1 3 so three electrons X X X

  5. sodium atom X X X X X X X X X atomic number X X Na 2 , 8 , 1 11 so eleven electrons X X X X X X X X X X X

  6. calcium atom X X X X X X X X X X X X X X X X atomic number X X X X Ca 2 , 8 , 8 ,2 20 so twenty electrons X X X X X X X X X X X X X X X X X X X X

  7. calcium ion X X X X X X X X X X X X X X atomic number X X X X 2+ 2+ 2+ Ca [ ] 2 , 8 , 8 20 positive ion so 20-2 electrons = 18 X X X X X X X X X X X X X X X X X X

  8. magnesium ion X X X X X X X X atomic number X X 2+ 2+ 2+ Mg [ ] 2 , 8 12 positive ion so 12-2 electrons = 10 X X X X X X X X X X

  9. chloride ion X X X X X X X X X X X X X X atomic number X X X X - - - Cl [ ] 2 , 8 , 8 17 negative ion so 17+1 electrons = 18 X X X X X X X X X X X X X X X X X X

  10. oxide ion X X X X X X X X atomic number X X 2- 2- 2- O [ ] 2 , 8 8 negative ion so 8+2 electrons = 10 X X X X X X X X X X

  11. electron shells (atom)

  12. electron shells (ion)

  13. References Steve Lewis for the Royal Society of Chemistry

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