Overview of Atoms in Chemistry

Structure of an Atom

• Nucleus: Center of the atom containing:
  • Protons: Positively charged (+1), relative mass of 1.
  • Neutrons: Neutral charge, relative mass of 1.
• Electrons: Orbit in shells around the nucleus, negatively charged (-1), about 2000 times smaller than protons or neutrons.

Periodic Table and Nuclear Symbols

• Elemental Symbol: Represents the element (e.g., Li for Lithium).
• Atomic Number: Bottom left of the box, indicates the number of protons.
  • Determines the element identity.
• Mass Number: Top left, total number of protons and neutrons.
  • Example: Lithium has a mass number of 7 (3 protons + 4 neutrons).
• Electrons Count: Equal to protons in a neutral atom.

Isotopes

• Definition: Atoms of the same element with the same number of protons but different numbers of neutrons.
• Example for Lithium:
  • Lithium-7: 3 protons, 4 neutrons.
  • Lithium-6: 3 protons, 3 neutrons.
  • Lithium-8: 3 protons, 5 neutrons.
• Stability:
  • Typically, only one or two isotopes are stable.
  • Unstable isotopes undergo radioactive decay, emitting radiation or neutrons.

Electron Energy Levels

• Energy Levels/ Shells: Electrons are arranged in shells, each further from the nucleus and higher in energy.
• Excitation:
  • Electrons can jump to a higher energy level if they gain enough energy from electromagnetic radiation.
  • They return to lower energy levels, re-emitting energy as electromagnetic radiation.

Ionization

• Process:
  • An outer electron gains enough energy to leave the atom, forming a positive ion.
  • Leaves atom with more protons than electrons, resulting in a positive charge.
• Ionizing Radiation: Capable of knocking electrons off atoms, thus ionizing them.

Conclusion

• Review of key topics about atoms including structure, isotopes, electron energy levels, and ionization.
• Encouragement to like and subscribe for more content.