Atomic Mass, Bohr and Lewis Diagrams PDF

ATOMIC MASS, BOHR AND LEWIS DIAGRAMS INTRODUCTION TO 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 CALCULATI...

ATOMIC MASS, BOHR AND LEWIS DIAGRAMS INTRODUCTION TO 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 = (number of protons + number of neutrons) × mass of proton/neutron Example: Carbon-12 6 protons + 6 neutrons = 12 nucleons Atomic mass ≈ 12 amu Electrons contribute very little to atomic mass due to their small size BOHR MODEL: A PLANETARY VIEW OF ATOMS Depicts atoms Electrons orbit Developed by as a small, the nucleus in Niels Bohr in positively fixed energy 1913 charged levels (shells) nucleus Helps explain Each shell can electron hold a specific behavior and number of energy electrons transitions   Oxygen atom (8 protons, 8 neutrons, 8 electrons) BOHR  Nucleus at center with 8 protons and 8 DIAGRAM neutrons  First shell: 2 electrons EXAMPLE:  Second shell: 6 electrons OXYGEN  Demonstrates how electrons are distributed in shells LEWIS DIAGRAMS: VALENCE ELECTRONS  Developed by Gilbert N. Lewis  Focus on valence electrons (outer shell)  Use dots to represent valence electrons  Element symbol surrounded by dots  Helps visualize electron sharing in chemical bonds CREATING LEWIS DIAGRAMS Steps: Example: Nitrogen Determine the number of valence (N) 5 valence electrons electrons Lewis diagram: N with 5 dots Write the element symbol around it Place dots around the symbol (up to 8) Arrange dots on four sides (single, then pairs) LEWIS  Show how atoms share electrons to form molecules DIAGRAMS  Dots become lines in covalent bonds AND  Example: Water (H₂O)  CHEMICAL Oxygen shares one electron with each hydrogen  Result: H-O-H BONDING COMPARING BOHR AND LEWIS DIAGRAMS Bohr Diagram:  Shows all electrons in shells  Depicts nucleus and overall structure Lewis Diagram:  Focuses on valence electrons  Useful for showing chemical bonding Both help us understand atomic structure and behavior! REVIEW AND KEY POINTS  Atomic mass: Total mass of an atom's particles  Bohr model: Electrons in fixed energy levels around nucleus  Lewis diagrams: Represent valence electrons with dots  Both models help us understand atomic structure and bonding  These concepts are crucial for chemistry and physical sciences