Section 3: The Quantum Mechanical Model of the Atom

These illustrations show how the atomic model has changed as scientists learned more about the atom’s structure.

Bohr's Model of the Atom (cont.) Bohr’s model explained the hydrogen’s spectral lines, but failed to explain any other element’s lines. The behavior of electrons is still not fully understood, but it is known they do not move around the nucleus in circular orbits. Section 5-2

The Quantum Mechanical Model of the Atom Louis de Broglie (1892–1987) hypothesized that particles, including electrons, could also have wavelike behaviors. Section 5-2

The Quantum Mechanical Model of the Atom (cont.) Heisenberg showed it is impossible to take any measurement of an object without disturbing it. The Heisenberg uncertainty principle states that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time. The only quantity that can be known is the probability for an electron to occupy a certain region around the nucleus. Section 5-2

The Heisenberg Uncertainty Principle The Heisenberg uncertainty principle states that it is impossible to know exactly both the velocity and the position of a particle at the same time. Quantum Mechanics

The Quantum Mechanical Model of the Atom (cont.) Schrödinger treated electrons as waves in a model called the quantum mechanical model of the atom. Schrödinger’s equation applied equally well to elements other than hydrogen. Section 5-2

…you cannot tell its exact location at any instant. The Quantum Mechanical Model of the Atom propeller has equal probability of being anywhere in the blurry region, but… …you cannot tell its exact location at any instant. The electron cloud of an atom is compared here to photographs of a spinning airplane propeller. a) The airplane propeller is somewhere in the blurry region it produces in this picture, but the picture does not tell you its exact position at any instant. b) Similarly, the electron cloud of an atom represents the locations where an electron is likely to be found.

The Quantum Mechanical Model of the Atom (cont.) The wave function predicts three-dimensional regions of probability where electrons are likely to be found. Section 5-2

Hydrogen Atomic Orbitals n specifies the atom’s major energy levels, called the principal energy levels. Section 5-2

Hydrogen Atomic Orbitals (cont.) Energy sublevels are contained within the principal energy levels. Section 5-2

Hydrogen Atomic Orbitals (cont.) Each energy sublevel relates to orbitals of different shape. Atomic Orbitals are 3-dimensional regions with a high probability of electrons Section 5-2

There is one s orbital, which is spherical. Atomic Orbitals There is one s orbital, which is spherical. The electron clouds for the s orbital and the p orbitals are shown here. There are three p orbitals, which are dumbbell-shaped. Atomic Orbitals

There are five d orbitals; four are shaped like clover-leafs Atomic Orbitals There are five d orbitals; four are shaped like clover-leafs and one is shaped like a dumbbell with a donut around the middle. The d orbitals are illustrated here. Four of the five d orbitals have the same shape but different orientations in space. Interpreting Diagrams How are the orientations of the dxy and dx2 – y2 orbitals similar? How are they different? Atomic Orbitals

There are seven f orbitals. 5.1 Atomic Orbitals The d orbitals are illustrated here. Four of the five d orbitals have the same shape but different orientations in space. Interpreting Diagrams How are the orientations of the dxy and dx2 – y2 orbitals similar? How are they different? There are seven f orbitals. Atomic Orbitals

The numbers and kinds of atomic orbitals depend on the energy sublevel.

The number of electrons allowed in each of the first four energy levels are shown here. Max # of e- = 2n2 Atomic Orbitals

A B C D Section 5.2 Assessment Which atomic suborbitals have a “dumbbell” shape? A. s B. f C. p D. d A B C D Section 5-2

A B C D Section 5.2 Assessment Who proposed that particles could also exhibit wavelike behaviors? A. Bohr B. Einstein C. Rutherford D. de Broglie A B C D Section 5-2