Key Concepts of Atomic Structure to Know for Physical Science

Understanding atomic structure is key in Physical Science, as it reveals how atoms are built and interact. This includes the roles of protons, neutrons, and electrons, as well as concepts like atomic number, isotopes, and electron configurations.

1. Atomic structure: protons, neutrons, electrons

   • Protons are positively charged particles found in the nucleus of an atom.
   • Neutrons are neutral particles, also located in the nucleus, contributing to atomic mass.
   • Electrons are negatively charged particles that orbit the nucleus in electron shells.

2. Atomic number and mass number

   • The atomic number is the number of protons in an atom, determining the element's identity.
   • The mass number is the total number of protons and neutrons in the nucleus.
   • Atomic number defines the position of an element in the periodic table.

3. Isotopes

   • Isotopes are variants of the same element with the same number of protons but different numbers of neutrons.
   • They have the same chemical properties but different physical properties, such as mass.
   • Some isotopes are stable, while others are radioactive and decay over time.

4. Electron shells and energy levels

   • Electron shells are regions around the nucleus where electrons are likely to be found.
   • Each shell corresponds to a specific energy level, with the first shell being the lowest energy.
   • The maximum number of electrons in a shell is determined by the formula 2n², where n is the shell level.

5. Bohr model of the atom

   • The Bohr model depicts electrons orbiting the nucleus in fixed paths or energy levels.
   • Electrons can jump between levels by absorbing or emitting energy in the form of photons.
   • This model explains the quantized nature of electron energy levels.

6. Valence electrons

   • Valence electrons are the outermost electrons in an atom and are involved in chemical bonding.
   • The number of valence electrons determines an element's reactivity and bonding behavior.
   • Elements in the same group of the periodic table have similar valence electron configurations.

7. Ion formation

   • Ions are charged particles formed when atoms gain or lose electrons.
   • Cations are positively charged ions formed by losing electrons, while anions are negatively charged ions formed by gaining electrons.
   • Ion formation is crucial for chemical reactions and the creation of compounds.

8. Atomic orbitals

   • Atomic orbitals are regions in space where there is a high probability of finding an electron.
   • They are defined by specific shapes (s, p, d, f) and energy levels.
   • Each orbital can hold a maximum of two electrons with opposite spins.

9. Quantum numbers

   • Quantum numbers describe the properties of atomic orbitals and the electrons within them.
   • There are four quantum numbers: principal (n), angular (l), magnetic (m), and spin (s).
   • These numbers provide information about the energy level, shape, orientation, and spin of electrons.

10. Electron configuration

    • Electron configuration is the distribution of electrons among the various orbitals of an atom.
    • It follows the Aufbau principle, Pauli exclusion principle, and Hund's rule.
    • The configuration helps predict an element's chemical properties and reactivity.