Atomic Structure: Subatomic Particles and Atomic Models

Atomic Structure

Subatomic Particles

• Proton: Positively charged, found in the nucleus, mass = 1 amu (atomic mass unit)
• Neutron: No charge, found in the nucleus, mass = 1 amu
• Electron: Negatively charged, found in energy levels, mass = 0.00055 amu

Atomic Models

• Rutherford Model (1911): Nucleus with electrons orbiting around it
  • Positively charged nucleus with negatively charged electrons
• Bohr Model (1913): Energy levels with electrons jumping between them
  • Electrons occupy specific energy levels (shells) around the nucleus

Atomic Structure Notation

• Atomic Number (Z): Number of protons in an atom's nucleus
• Mass Number (A): Sum of protons and neutrons in an atom's nucleus
• Electron Configuration: Arrangement of electrons in energy levels
  • Notation: 1s² 2s² 2p⁶ (example)

Energy Levels (Shells)

• Principal Energy Levels (n): 1, 2, 3, ... (distance from nucleus increases)
• Subshells (l): s, p, d, f (shapes of orbitals)
• Orbitals: Regions where electrons are likely to be found
  • s-orbitals: spherical shape
  • p-orbitals: dumbbell shape
  • d-orbitals: four-leaf clover shape
  • f-orbitals: complex shape

Atomic Structure

Subatomic Particles

• A proton has a positive charge and is found in the nucleus with a mass of 1 atomic mass unit (amu).
• A neutron has no charge and is found in the nucleus with a mass of 1 amu.
• An electron has a negative charge and is found in energy levels with a mass of 0.00055 amu.

Atomic Models

Rutherford Model (1911)

• The nucleus is positively charged, and electrons orbit around it.
• The model consists of a positively charged nucleus with negatively charged electrons.

Bohr Model (1913)

• Electrons occupy specific energy levels (shells) around the nucleus.
• Electrons jump between energy levels, and each energy level has a specific capacity.

Atomic Structure Notation

• The atomic number (Z) is the number of protons in an atom's nucleus.
• The mass number (A) is the sum of protons and neutrons in an atom's nucleus.
• Electron configuration is the arrangement of electrons in energy levels.
• Electron configuration notation is used to describe the arrangement, such as 1s² 2s² 2p⁶.

Energy Levels (Shells)

• Principal energy levels (n) are numbered from 1, 2, 3, and so on, with increasing distance from the nucleus.
• Subshells (l) are classified as s, p, d, and f, and they have different shapes of orbitals.
• Orbitals are regions where electrons are likely to be found, with different shapes:
  • s-orbitals are spherical in shape.
  • p-orbitals have a dumbbell shape.
  • d-orbitals have a four-leaf clover shape.
  • f-orbitals have a complex shape.

Atomic Structure

Subatomic Particles

• Protons have a positive charge and are found in the nucleus, determining the element through their atomic number.
• Neutrons have no charge and are found in the nucleus, contributing to the atomic mass along with protons.
• Electrons have a negative charge and are found in energy levels outside the nucleus, with their number equal to the number of protons in a neutral atom.

Energy Levels (Shells)

• Electron configuration refers to the arrangement of electrons in energy levels.
• The valence shell is the outermost energy level, determining the chemical properties of an atom.
• The Aufbau principle states that electrons occupy the lowest available energy level.
• Pauli's Exclusion Principle states that each electron has a unique set of quantum numbers.

Atomic Orbitals

• s orbitals have a spherical shape, with one orbital per energy level.
• p orbitals have a dumbbell shape, with three orbitals per energy level (x, y, z).
• d orbitals have a complex shape, with five orbitals per energy level.
• f orbitals have a complex shape, with seven orbitals per energy level.

Electron Configuration Notation

• Shorthand notation represents the number of electrons in each orbital (e.g., 1s² 2s² 2p⁶).
• Block notation groups orbitals (s, p, d, f) with the number of electrons in each.

Periodic Trends

• Atomic radius decreases from left to right across a period and increases from top to bottom in a group.
• Electronegativity increases from left to right across a period and decreases from top to bottom in a group.
• Ionization energy increases from left to right across a period and decreases from top to bottom in a group.