1. The Nature of Electrons

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

3. 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!

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

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

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

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

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

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

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

12. Energy yeah baby!

13. 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)

14. 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!

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

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

17. 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”

18. nucleus
electron in ground state
that emitted light energy

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

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

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

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

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

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

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

28. 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)

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