Study guide: Atomic Structure and Periodic Patterns

📋 Course Outline

1. Models of Atomic Structure
2. Electron Shells and Configurations
3. Valence Electrons and Reactivity
4. Periodic Table Patterns
5. Atomic Number and Mass
6. Electron Energy and Light
7. Properties of Metals

📖 1. Models of Atomic Structure

📝 Essential Points

• In the Bohr model, electrons circle the nucleus only in allowed paths.

• The quantum mechanical model represents electrons in three-dimensional areas around the nucleus.

💡 Memory Hook

Bohr’s allowed paths contrast with the quantum model’s three-dimensional electron regions.

📖 2. Electron Shells and Configurations

★ Must-know

• An orbital can hold up to two electrons.

Further detail

• The first subshell, 1s, has the lowest energy and contains one spherical orbital.

• The second energy shell has two subshells, labeled s and p.

• An atom can have a maximum of seven energy levels.

• The electron configuration of potassium, which has 19 electrons, is 2, 8, 8, 1.

📖 3. Valence Electrons and Reactivity

★ Must-know

• Valence electrons are responsible for an atom’s chemical properties.

Further detail

• Electron-dot notation shows only the valence electrons in an atom’s outermost energy shell.

• Valence electrons are involved in chemical reactions.

• Elements with a full outer energy shell are typically unreactive.

💡 Memory Hook

Outer-shell electrons shape chemical properties and chemical reactions.

📖 4. Periodic Table Patterns

📝 Essential Points

• Elements can be organized into periodic-table rows and columns by patterns in properties such as metallic or nonmetallic character, solid or gas state, and reactivity.

• The periodic table can be used to predict relative element properties from patterns in the electrons in atoms’ outermost energy levels.

📖 5. Atomic Number and Mass

★ Must-know

📌 The mass number counts an atom’s protons and neutrons, whereas average atomic mass is a weighted average of the masses of its isotopes.

• A strontium atom with atomic number 38 and mass number 88 has 38 protons, 50 neutrons, and 38 electrons.

Further detail

• Chlorine has 17 electrons in total and 7 valence electrons because only the electrons in its outermost energy shell are valence electrons.

💡 Memory Hook

Mass number counts protons and neutrons; average atomic mass averages isotope masses.

📖 6. Electron Energy and Light

★ Must-know

• When electrons in atmospheric gases absorb energy, they can move to higher energy states; when they return to their original energy levels, they release energy as light.

• The color of light emitted by an element depends on its specific arrangement of energy levels.

Further detail

• Different metallic elements give off different colors when burned in a flame.

• In flame tests, electrons in metal ions emit energy as they move from higher to lower energy levels.

💡 Memory Hook

Absorb energy → rise to a higher level → fall and emit light.

📖 7. Properties of Metals

★ Must-know

• Shininess and good electrical conductivity are properties that support identifying an element as a metal.

Further detail

• Partial electrical conductivity is also listed as a property that can support identifying an element as a metal.