The Nature of Electrons

Scientists noticed when certain elements are placed in a flame, they emit light!

The light given off when an element is heated is called it’s atomic emission spectrum The atomic emission spectrum is a different color for every element!

The color is like the “signature” of that element It can be used to identify the element like a fingerprint can identify you!

No two elements have the same atomic emission spectrum!!!

Scientists began to wonder . . . Rutherford’s model is good, but it doesn’t explain some things

Rutherford’s model didn’t explain: why different elements react differently (and have different atomic emission spectra) 2. how electrons are arranged

The Planetary Atomic Model Neils Bohr Bohr worked with hydrogen and developed a new model of the atom: The Planetary Atomic Model

Bohr’s Planetary Atomic Model: electrons move around the nucleus in circular “orbits” (paths) much like planets orbit the sun

Each “orbit” has a certain level of energy smaller orbits = lower energy larger orbits = higher energy

Energy . . . yeah baby!

electrons are able to change energy levels one at a time (like climbing the rungs of a ladder) The LOWEST energy level available is called the ground state (it is the closest to the nucleus)

As an electron “jumps” from a low energy level to a higher one, it needs to absorb energy and become “excited” like you would need energy to “jump” up high!

nucleus ground state electron that absorbed energy and is “excited”

once an electron is “excited” and in a higher energy level, it can’t stay there because it’s not the “home orbit”

An electron will “drop” to a lower energy level Every time an electron drops levels, it emits light – this is the light that we see when we put an element into a flame! The electrons release the energy before they go “home”

nucleus electron in ground state that emitted light energy

Bohr worked to discover all of this, but keep in mind that he only worked with hydrogen!

Scientists thinkin’ again . . . If opposite charges attract, then why are negative electrons (that are lighter) not pulled into the positive nucleus?????

Well . . . It all has to do with energy – the energy of motion! electrons actually “wiggle” as they move around the nucleus

DeBroglie’s Wave Theory DeBroglie proposed that electrons move like waves around the nucleus

Heisenberg Heisenberg’s Uncertainty Principle: it is impossible to know the exact position of an electron (if they travel in waves)

The Quantum Mechanical Model 1. developed by Schrödinger 2. atoms have a dense, positively charged nucleus

3. electrons surround the nucleus and are treated as waves, not particles

There is a GOOD probability of finding an electron in an atomic orbital **an atomic orbital is a three-dimensional region around the nucleus (it’s not an orbit)

Was it the worst day of your life? You made it! Was it the worst day of your life? PPT by Leann Foxworth Thanks