1. Announcements Be respectful – no electronics please!
Pre/post lecture assignments due as usual Tuesdays & Thursdays at 8:00 am
Textbook homework due tomorrow in discussion
“Workshop” in lab on Monday: Bring a textbook!
Clicker #1 Review from Tuesday:
Which of the following is an endothermic process?
A) A solid becoming a liquid
B) Water vapor condensing
C) A match burning
D) Liquid water freezing
E) All are endothermic processes

2. Various Atomic Models
Dalton: Law of Definite Proportions. (He concludes that atoms are indivisible and have mass.)

3. Various Atomic Models
Dalton: Law of Definite Proportions. (He concludes that atoms are indivisible and have mass.)

4. Various Atomic Models
Dalton: Law of Definite Proportions. (He concludes that atoms are indivisible and have mass.)
J.J. Thompson: atoms emit tiny negative particles. (Therefore atoms not indivisible!)

5. Various Atomic Models
Dalton: Law of Definite Proportions. (He concludes that atoms are indivisible and have mass.)
J.J. Thompson: atoms emit tiny negative particles. (Therefore atoms not indivisible!)
William Thompson: formulates the Plum Pudding Model. (Electrons moving in a positively charged cloud.)

6. Various Atomic Models
Dalton: Law of Definite Proportions. (He concludes that atoms are indivisible and have mass.)
J.J. Thompson: atoms emit tiny negative particles. (Therefore atoms not indivisible!)
William Thompson: formulates the Plum Pudding Model. (Electrons moving in a positively charged cloud.)
Rutherford: Some α-particles bounce back when shot at atoms. (There is a concentration of mass with a positive charge in the atom – the nucleus.)

7. Clicker #2
How many of the following statements about atomic theory are still believed to be true?
I. All atoms of the same element are identical.
II. Negatively charged particles are embedded in a positively charged cloud throughout the atom.
III. As verified by Rutherford, only positively charged particles called protons are found inside the nucleus.
IV. J.J. Thomson provided the first experimental support for the atom.
A) B) 1 C) 2 D) E) 4

8. Niels Bohr Model

9. Take Homes: Niels Bohr Model
Electrons:
Organized in discrete, quantized energy levels positioned outside the nucleus of the atom.
Naturally positioned as close to the nucleus of the atom as possible (ground state.)
Can move from one energy level to a higher level with the addition of energy, but are never located between levels.
The positioning of energy levels and the number of electrons is unique for each element.

10. Take Homes: Niels Bohr Model
Adding energy to an electron excites it, making it move further from the nucleus of the atom.
To regain stability, an electron releases energy (often in the form of light) to return it to a lower energy level.
Electrons orbit the nucleus of the atom in fixed paths.

11. Electromagnetic Radiation: Visible Spectrum

12. Electromagnetic Radiation: Visible Spectrum

13. (resistance through a wire)
Example: Light Bulb
Energy as
Light and Heat
Heating Wire
(resistance through a wire)

14. Clicker #3 When an electron is excited in an atom or ion
A) the electron moves further from the nucleus.
B) only specific quantities of energy are released in order for the electron to return to its ground state.
C) white light is never observed when the electron returns to its ground state.
D) the electron is only excited to certain energy levels.
E) All of the above statements are true when an electron is excited.

15. Electrons Electrons are most likely to be found near the nucleus
Electrons could be anywhere (very far even)
We do not know how the electron moves
ORBITALS = regions of 90% probability