4.3 - Modern Atomic Theory

Modern Atomic Theory

-An electron cloud is a visual model of the most likely locations for electrons in an atom. -The cloud is denser at those locations where the probability of finding an electron is high.

Electrons & Energy Levels

-An electron in an atom can move from one energy level to another when the atom gains or loses energy. -The size of the jump between energy levels determines the amount of energy gained or lost.

Atomic Orbitals

-An orbital is a region of space around the nucleus where an electron is likely to be found. -The electrons cloud represents all the orbitals in an atom.

Niels Bohr - 1913

-Bohr's model focused on the electrons. Energy Level - the possible energies that electrons in an atom can have. -In Bohr's model electrons move (with constant speed in fixed orbits around the nucleus). Like planets around a sun.

James Chadwick - 1932

-Confirms the existence of neutrons. -Have a neutral charge.

Bohr's Model & Energy Levels

Advanced Bohr Model - the electron orbits were still like planets orbiting the sun, but they were also assigned energy levels and could move from level to level.

Excited state

less stable configuration, when electrons gain energy and move to a higher energy level or orbital.

Ground state

most stable configuration, electrons are in the lowest possible energy levels.