Atomic Mass and Bohr Model Quiz

Atomic Mass

• Atomic mass is the total mass of protons, neutrons, and electrons in an atom.
• Measured in atomic mass units (amu).
• 1 amu ≈ 1.66 × 10^-24 grams
• Important for understanding chemical reactions and element properties.

Calculating Atomic Mass

• Atomic mass is calculated by adding the number of protons and neutrons and multiplying by the mass of a proton or neutron.
• Protons and neutrons have almost the same mass, approximately 1 amu.
• Electrons have a very small mass and contribute minimally to the total atomic mass.

Bohr Model

• Developed by Niels Bohr in 1913.
• Depicts atoms as a positively charged nucleus surrounded by electrons orbiting in fixed energy levels (shells).
• Each shell can hold a specific number of electrons.
• Helps explain the behavior and energy transitions of electrons.

Bohr Diagram Example: Oxygen

• Oxygen has 8 protons, 8 neutrons, and 8 electrons.
• Nucleus contains 8 protons and 8 neutrons.
• First shell: 2 electrons
• Second shell: 6 electrons
• Demonstrates electron distribution in shells.

Lewis Diagrams

• Developed by Gilbert N. Lewis.
• Focus on valence electrons (outermost shell electrons).
• Use dots to represent valence electrons around the element symbol.
• Helps visualize electron sharing in chemical bonds.

Creating Lewis Diagrams

• Determine the number of valence electrons for the specific element.
• Write the element symbol.
• Place dots around the symbol, representing valence electrons.
• Arrange dots on four sides (single dots first, then pairs).

Lewis Diagrams and Chemical Bonding

• Show how atoms share electrons to form molecules.
• Dots become lines in covalent bonds.
• Example: Water (H₂O)
• Oxygen shares one electron with each hydrogen atom resulting in the structure H-O-H.

Comparing Bohr and Lewis Diagrams

• Bohr Diagrams: Show all electrons in their respective shells, including the nucleus, and provide an overall structure of the atom.
• Lewis Diagrams: Focus on valence electrons and are useful for demonstrating chemical bonding.
• Both models contribute to understanding atomic structure and behavior.

This quiz explores the concept of atomic mass, how it is calculated, and the Bohr model of the atom. You'll learn about protons, neutrons, and electrons, as well as how these particles contribute to the structure and energy levels of atoms. Test your understanding of these fundamental chemistry concepts!