7.1 Expanding Theory of the Atom

Lorena María Wheelock Gutiérrez

Electrons don’t behave like other objects, they are too small, they move so fast, and they seem to be in

perpetual motion.

The Atomic Model Through Years

1803

Dalton’s Model

1897

Thomson’s Model

1911

Rutherford’s Model

1913

Bohr’s Atomic Model

Today’s Model

P: +

E: -

Protons and neutrons form the center of the atom, and electrons

are distributed around the nucleus.

Electrons with the most energy are farther from the

nucleus and occupy the outermost energy

level

Modern Atomic Model

Niels Bohr

When he was 28 he developed his atomic theory. Then 9 years later he received the Nobel Price

in Physics for this work.His basic ideas of his theory

were:–Electrons move around the

atom’s nucleolus in circular paths called orbits.

-Orbits are definite distances from the nucleus and represent

energy levels that determine the energies of the electrons.

-The nearest orbits to the nucleus have less energy and the farthest

have more energy.-If electrons absorb energy they move to another energy level, a highest one, so when the drop to a lower energy level, the energy

is release.-Energy is absorbed and given off

in definite amounts called quanta.

(1885-1962)

Bohr’s Atomic Theory

There’s a close relationship between the electrons, and

the periodic table arrangement. Because the

number of valence electrons is the same for all the groups, as in the next

table…

All elements have an electron distribution, over a range of

energy levels, according to the periodic table of elements.

Here we have an example… Sulfur (S), energy level like, 2e-,

8e- and 6e-.

Valence Electrons

and

Periodic Table

Electromagnetic Radiation and Energy

Here is a common Bohr diagram, but when we add energy…

The number of energy level that an electron jumps depends on the

amount of energy that it absorbs. When a electron falls back, it’s his

original level.

Comparison and Emission of an Spectra

The Big gaps between the spectrum lines said that the electrons are moving between energy levels that have a large difference in energy…

The existence of sublevels within a energy level can explain the fine lines in the spectra of these elements.

Here is an example, there’s showing the relative energies such as, 1s, 2s, 1p, 2p,3s,3p and 3b

sublevels.

Electrons in the 1s sublevels are closest to the nucleus.

Electrons in the 3s, 3p, and 3d sublevels are the farthest from the nucleus.

Electron Distribution in an Atom