Ch. 5 Sections 1&2

John Dalton pictures atoms as tiny, indestructible particles, with no i termal structure.

1803

JJ Thomson, a British scientist, discovers the electron. The later leads to his *plum-pudding* model. He pictures electrons embedded in a sphere of positive electrical charge

1897

Ha taro Magaoka, a Japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn.

1904

New Zealand physicists Ernest Rutherford finds that an atom has a small, dense, positively charged nucleus. Electrons move around the nucleus.

1911

In Niels Bohr's model, the electron moves in a circular orbit at fixed distances from the nucleus.

1913

French physicist Louis de Broglie proposes that moving particles like electrons have some properties of waves. Within a few years, experimental evidence supports the idea.

1923

Erwin Schrodinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model.

1926

James Chadwick, an English physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.

1932

letters

Different atomic orbitals are denoted by ?

fixed energy

Each possible electron orbit in Bohr's model has a ?

subtle electron-electron interactions in orbitals with very similar energies.

Exceptions to the aufbau principle are due to

different orientations in space.

Four of the five d orbitals have the same shape but ?

Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

How do sublevels of principal energy levels differ?

true

In the quantum mechanical model, the probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloud.

The electron cloud

Is a visual model of the probable locations of electrons in an atom. The probability of finding an electron is in the denser regions of the cloud.

true

Like the rungs of the strange ladder, the energy levels in an atom are not equally spaced.

why objects change color when heated.

Rutherford's atomic model could not explain:

the probability of finding the electron is high.

The cloud is more dense where ?

spinning airplane propeller.

The electron cloud of an atom can be compared to a?

energy levels

The fixed energies an electron can have are called

the less energy it takes to move from that energy level to the next higher energy level.

The higher the energy level occupied by an electron

quantum mechanical model,

The modern description of the electrons in atoms comes from the mathematical solutions to the Schrödinger equation.

x2, x4, x6, x8 = 2,8,18,32

The number of electrons allowed in each of the four energy levels.

the energy sublevel

The numbers and kinds of atomic orbitals depend on

true

The propeller blade has the same probability of being anywhere in the blurry region, but you cannot tell its location at any instant.

true

The s orbitals are spherical, and p orbitals are dumbbell-shaped.

electron configurations

The ways in which electrons are arranged in various orbitals around the nuclei of atoms are called

the aufbau principle, the Pauli exclusion principle, and Hund's rule

Three rules that tell you how to find the electron configurations of atoms.

Three rules—the aufbau principle, the Pauli exclusion principle, and Hund's rule—tell you how to find the electron configurations of atoms.

What are the three rules for writing the electron configurations of elements?

The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus.

What does the quantum mechanical model determine about the electrons in an atom?

Rutherford's atomic model could not explain the chemical properties of elements.

What was inadequate about Rutherford's atomic model?

Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.

What was the new proposal in the Bohr model of the atom?

Some actual electron configurations differ from those assigned using the aufbau principle because half-filled sublevels are not as stable as filled sublevels, but they are more stable than other configurations.

Why do actual electron configurations for some elements differ from those assigned using the aufbau principle?

Pauli exclusion principle,

an atomic orbital may describe at most two electrons. To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired.

An electron

can gain or lose energy by changing its orbit.

aufbau principle

electrons occupy the orbitals of lowest energy first.

Copper

has an electron configuration that is an exception to the aufbau principle.

atomic orbital

is often thought of as a region of space in which there is a high probability of finding an electron.

A quantum of energy

is the amount of energy required to move an electron from one energy level to another energy level.

Hund's rule

states that electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible.

Austrian physicist Erwin Schrödinger (1887-1961)

used new theoretical calculations and results to devise and solve a mathematical equation describing the behavior of the electron in a hydrogen atom.