Notes on Drawing Elections and Electron Configuration

Drawing Elections

  • Nucleus: The central part of an atom.

    • Contains protons and neutrons.

  • Atomic Number: The number of protons in the nucleus of an atom.

  • Example 1:

    • Element: Silicon

    • Number of protons (P) = 14

    • Number of atomic weight= 28 (round up if necessary)

    • Number of electrons (e) = 14 (in a neutral atom)

    • To get the number of neutrons, subtract the number of protons from the mass number: \text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons} example 28 - 14 = 14 .

Electron Configuration

  • Electrons occupy different energy levels or shells around the nucleus.

  • Electron Shell Capacity:

    • 1st shell: can hold up to 2 electrons.

    • 2nd shell: can hold up to 8 electrons.

    • 3rd shell: can hold up to 8 electrons (but can hold more in larger atoms).

  • Filling Electron Shells: Electrons fill the innermost shells first.

  • Example 2: Silicon (Si)

    • Atomic weight = 28.0855

    • Number of protons = 14

    • Number of neutrons = 14 (28 - 14 = 14)

    • Electron configuration:

      • 1st shell: 2 electrons

      • 2nd shell: 8 electrons

      • 3rd shell: 4 electrons (2+8+4 = 14)