Models of the Atom

1. Models of the Atom

2. Development of the Atomic Model • Could Rutherford’s atomic model explain the chemical properties of an element? No, to describe the chemical properties of an element we needed a model that better describes the behavior of electrons.

3. The Bohr Model • Niels Bohr (1885 – 1962) – Danish Physicist/ Student of Rutherford • An electron is found only in specific circular paths, or orbits, around the nucleus. • The energy of an atom changes when it absorbs or emits light. • Each orbit has a fixed energy (each orbital is a different energy level.) • A quantum of energy is the amount of energy required to move from one energy level to another

4. The amount of energy that an electron loses or gains in an atom is not always the same. The energy levels in an atom are not evenly spaced. Why do you think that is? The further the electron is from the nucleus, the less energy it takes to move to the next level.

5. The Quantum Mechanical Model • Erwin Schrodinger (1887-1961) • Came up with an equation (Schrodinger equation) that described the behavior of the electron in a hydrogen atom. • The quantum mechanical model (electron cloud model): • The modern description of electrons in an atom • Determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus. • Based on probability

6. Atomic Orbitals • What does solving the Schrodinger equation show us? -The energies an electron can have • What do atomic orbitals show us? -The region of space where there is a high probability of finding an electron.

7. Atomic Orbitals (Continued) • n : Principal quantum numbers (principal energy levels) • n is assigned the value of (1,2,3,4,…) • Sub levels • For each principal energy level there are several sublevels with different shapes that indicate where an electron can be found

8. Atomic Orbitals (Continued) • Different atomic orbitals are denoted by different letters • s,p,d,f • s orbitals are spherical • p orbitals are dumbbell shaped • d orbitals are clover shaped (4 leaf) • f becomes complicated to explain and you won’t have to explain the shape.

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