Electron Arrangement

• What is the focus of today's video?

  Arrangement of electrons in atoms
• Why do most atoms have an incomplete outer shell?

  They need a full outer shell to be stable
• 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 around the nucleus
• 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 do you do when you run out of electrons?

  Put remaining electrons in the next shell
• Why is sodium considered unstable?

  It has one electron in its outer shell
• What do most atoms want to do to achieve stability?

  React to form molecules or compounds
• What do noble gases have in terms of electron configuration?

  Completely full outer shells
• What is the atomic number of argon?

  18
• How do you represent the electron structure of an atom?

  Using numbers like 2, 8, 8
• What is the electron structure of calcium?

  2, 8, 8, 2
• Why is calcium considered unstable?

  It has two electrons in its outer shell
• What happens when calcium loses two electrons?

  It becomes a calcium ion with a 2+ charge
• What is the atomic number of fluorine?

  9
• How many electrons does fluorine have?

  9 electrons
• What does fluorine need to become stable?

  Gain one more electron
• What charge does a fluoride ion have?

  Minus one charge
• How is the electron structure of fluoride represented?

  As 2, 7
• What are the key points about electron arrangement in atoms?

  • Atoms need a full outer shell to be stable.
  • Electrons are arranged in shells around the nucleus.
  • First shell holds 2 electrons, second holds 8, third holds 8.
  • Atoms react to achieve a full outer shell.
  • Noble gases have full outer shells and are stable.
• How do you determine the electron arrangement of an element?

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