Atomic Structure and Subatomic Particles

Atomic Structure

• Atoms are the fundamental building blocks of matter
• Matter is anything that occupies space and has mass
• Understanding atomic structure is key to understanding the properties of matter
• Atoms consist of subatomic particles: electrons, protons, and neutrons

Subatomic Particles

• Subatomic particles make up atoms
• Many subatomic particles exist but the three most important for chemistry are: electrons, protons, and neutrons
• Electrons have a negative charge
• Protons have a positive charge
• Neutrons have no charge

Properties of Subatomic Particles

Atomic Structure: Atom

• Atoms are electrically neutral because the number of protons equals the number of electrons
• Protons and neutrons are located in the nucleus of an atom
• Electrons orbit the nucleus

Atomic Number

• The atomic number identifies an element
• The atomic number equals the number of protons in an atom
• Example: Hydrogen's atomic number is 1, meaning it has 1 proton.

Mass Number

• Mass number is the sum of protons and neutrons in an atom
• Example: If an atom has a mass number of 3 and an atomic number of 1 (Hydrogen), it has 2 neutrons (3-1=2).
• The number of neutrons = mass number - atomic number

Determining the Number of Subatomic Particles

• Using the mass and atomic numbers, the number of protons, neutrons, and electrons can be calculated for any atom
• Example: Lithium (Li) has atomic number 3 and mass number 7 = 3 protons, 4 neutrons, 3 electrons.

Bohr's Model

• Atoms have a centrally located, positively charged nucleus containing protons and neutrons
• Electrons orbit the nucleus in specific energy levels or shells/orbits
• Each electron shell can only hold a specific number of electrons (2n²)

Bohr Model of the atom (2n²):

• The first shell can hold a maximum of 2 electrons
• The second shell can hold a maximum of 8 electrons
• The third shell can hold a maximum of 18 electrons

Electron Cloud Model

• The electron cloud represents the probability of finding an electron in a particular region around the nucleus
• The electron cloud model is a more complex and modern way of visualizing electron distribution compared to the Bohr model.
• Electrons exist in a cloud-like orbital around the nucleus
• Electrons are not confined to specific paths.

Quantum Numbers

• Quantum numbers describe the properties of atomic orbitals and the electrons within them
• Quantum numbers are used to characterize the energy levels, angular momentum, magnetic properties, and spin of each electron in an atom
• Four quantum numbers describe each electron:
  • Principal quantum number (n): indicates the main energy level of the electron
    • Angular momentum quantum number (l): describes the shape of the orbital
    • Magnetic quantum number (ml ): specifies the orientation of the orbital
  • Spin Quantum Number (s): the electron spin

Sublevel Names

Electron Configuration

• Describes the arrangement of electrons in an atom's energy levels and sublevels
• Electrons occupy orbitals following principles like the Aufbau principle (filling orbitals from lowest to highest energy), Hund's rule (filling orbitals evenly before pairing up electrons), and Pauli exclusion principle (no two electrons in the same atom can have the same set of four quantum numbers)

Isotopes

• Isotopes have the same number of protons but different numbers of neutrons
• Therefore, isotopes of an element have different mass numbers but same atomic number

Elements

• An element is a substance that is made entirely from one type of atom
• Scientists have identified 90 naturally occurring elements and made 28 more

Explore the fundamentals of atomic structure and the essential subatomic particles that make up atoms. This quiz covers the properties of electrons, protons, and neutrons, highlighting their charges and masses. Understanding these concepts is crucial for grasping the properties of matter.