Chapter 4: Structure of the Atom
Dear Atomic Explorers, Today we embark on one of science's greatest adventures - peering inside the atom! In my 25+ years of teaching, I've watched students' amazement when they realize that atoms are mostly empty space, yet everything we touch is made of them. We'll follow the footsteps of brilliant scientists who used ingenious experiments to "see" the invisible. Get ready to discover a world smaller than anything you can imagine, yet more fascinating than any science fiction!
Remember: Scientists couldn't actually "see" atoms, but they used clever experiments to understand their structure. This is the beauty of scientific thinking - using evidence to understand the invisible!
For over 2000 years, people believed atoms were indivisible (the word "atom" means "cannot be cut"). But in the late 1800s, scientists began discovering that atoms have internal structure! It was like finding out that what you thought was a solid marble actually contains an entire universe inside. Let's follow this incredible journey of discovery!
J.J. Thomson - The First Subatomic Particle
Goldstein & Rutherford - The Positive Particle
James Chadwick - The Neutral Particle
| Particle | Symbol | Charge | Mass (kg) | Location | Discoverer |
|---|---|---|---|---|---|
| Electron | eâ» | -1 | 9.1 Ă 10â»ÂłÂč | Outside nucleus | J.J. Thomson (1897) |
| Proton | pâș | +1 | 1.67 Ă 10â»ÂČâ· | In nucleus | Rutherford (1919) |
| Neutron | nâ° | 0 | 1.67 Ă 10â»ÂČâ· | In nucleus | Chadwick (1932) |
1. An atom has 17 protons, 18 neutrons, and 17 electrons. What is its atomic number, mass number, and electronic configuration?
Hint: Atomic number = protons, Mass number = protons + neutrons
2. Explain why Rutherford's gold foil experiment disproved Thomson's model.
Hint: Think about what the experiment revealed about atomic structure
3. Carbon-12 and Carbon-14 are isotopes. Explain why they have the same chemical properties but different physical properties.
Hint: Consider what determines chemical vs physical properties
"Tom's Pudding, Ruth's Nucleus, Bohr's Orbits" - Remember the evolution!
Always fill K shell first (max 2), then L shell (max 8), then M shell
Same protons = same element, different neutrons = different mass
Max electrons in shell:
2nÂČ
Mass number:
A = pâș + nâ°
Atomic number:
Z = pâș = eâ»
Neutrons:
nâ° = A - Z
We'll explore the cell - the basic unit of all living things!
Preview: How are plant and animal cells different? What makes a cell alive?