Electron Configuration

• What is the focus of today's video?

  Arrangement of electrons in atoms
• Why do most atoms need a full outer shell?

  To achieve stability
• What happens if an atom has an incomplete outer shell?

  It reacts with another atom
• What is the atomic number of sodium?

  11
• How many protons does sodium have?

  11 protons
• How are electrons arranged around the nucleus?

  In shells or energy levels
• How many electrons can the first shell hold?

  2 electrons
• How many electrons can the second shell hold?

  8 electrons
• What is the best way to add electrons to the shells?

  In top, right, bottom, left positions
• What happens when you fill the shell with electrons?

  You add them in clockwise order
• How many electrons does sodium have in its outer shell?

  1 electron
• What do most atoms want to do to achieve stability?

  React to form molecules or compounds
• Why is sodium considered unstable?

  It has an incomplete outer shell
• What do noble gases have in terms of electron configuration?

  Completely full outer shells
• Why don't noble gases react with other elements?

  They have full outer shells
• How do you determine the electron arrangement of argon?

  Find its atomic number, which is 18
• What is the electron structure of argon?

  2, 8, 8
• How many electrons does calcium have?

  20 electrons
• Why is calcium considered unstable?

  It has an incomplete outer shell
• What is the electron structure of calcium?

  2, 8, 8, 2
• What happens when calcium loses two electrons?

  It becomes a calcium ion with a +2 charge
• How do we denote ions in diagrams?

  With square brackets and charge
• What is the atomic number of fluorine?

  9
• How many electrons does fluorine have in its outer shell?

  7 electrons
• What does fluorine need to become stable?

  Gain one more electron
• What charge does fluorine have when it gains an electron?

  -1 charge
• How is the electron structure of fluoride written?

  2, 8
• What are the key points about electron arrangements in atoms?

  • Atoms need a full outer shell for stability
  • Electrons are arranged in shells around the nucleus
  • First shell holds 2 electrons, second holds 8, third holds 8
  • Atoms react to achieve full outer shells
  • Noble gases have full outer shells and are unreactive
• How do you calculate the electron arrangement for the first 20 elements?

  1. Identify the atomic number
  2. Draw the nucleus
  3. Fill the first shell (2 electrons)
  4. Fill the second shell (8 electrons)
  5. Fill the third shell (8 electrons)
  6. Write the structure as numbers (e.g., 2, 8, 8)