Electron Shells

• What do electrons occupy in an atom?

  Electrons occupy shells (or energy levels).
• How do electron shells differ from snail shells?

  Electrons do not nibble on plants like snails do.
• What are the rules for filling electron shells?

  1. The lowest energy levels are filled first.
  2. Maximum electrons per shell:

  • 1st shell: 2 electrons
  • 2nd shell: 8 electrons
  • 3rd shell: 8 electrons
• How many electrons can the first shell hold?

  The first shell can hold 2 electrons.
• How many electrons can the second shell hold?

  The second shell can hold 8 electrons.
• What is the electronic structure of nitrogen?

  The electronic structure of nitrogen is 2.5.
• How many protons does nitrogen have?

  Nitrogen has seven protons.
• What does the periodic table indicate about an element's electrons?

  The periodic table indicates the number of protons, which equals the number of electrons in a neutral atom.
• How do you determine the electronic structure of an element?

  You follow the electron shell rules based on the number of protons.
• How does the electronic structure of argon look based on its protons?

  The electronic structure of argon is 2.8.8.
• How can you determine the number of shells and outer shell electrons of an element from the periodic table?

  • The number of shells is equal to the period of the element.
  • The group number indicates how many electrons are in the outer shell.
• What is the electronic structure of sodium based on its period and group?

  The electronic structure of sodium is 2.8.1.
• How many protons does sodium have?

  Sodium has 11 protons.
• What is the maximum number of electrons in the third shell?

  The maximum number of electrons in the third shell is 8.
• Why is it easy to work out the electronic structure of elements?

  Because the rules for filling electron shells are straightforward.