Atoms = building blocks of mass.
y Atoms are mostly nothing.
Atoms = building blocks of mass.
The Atomic Nature of Matter
PH 104 w/ dr. g
Lec 12
y EVERYTHING = combos of only 100+ elements
y Combos = molecules, compounds, mixtures
y (Where is the antimatter and dark matter?)
Atoms = building blocks of mass.
Atoms are mostly nothing.
• Small: Too tiny to be resolved by visible light waves…
• Numerous:
• Always moving: travelling, vibrating,
• Positive nucleus, negative electrons, and a lot of nothing
• Nucleus: carries the mass: neutrons (no charge) and protons
• Electron: 10,000 times lighter, but same charge as proton
• Electrically neutral: number of electrons = number of protons
• Distance from electron to nucleus: about 105 nuclei
• Distance from Earth to sun: only ~100 suns
• Pluto to sun: about 5000 suns!
• 105 sun diameters ~ 20 x farther than Pluto
Atoms = building blocks of mass.
Atoms = building blocks of mass.
EVERYTHING = combos of only 100+ elements
Combos = molecules, compounds, mixtures.
y Element = substance made of identical atoms (one kind)
y Periodic Table: calendar listing of all 112 known elements
y Grouped by distribution of electrons in up to 7 shells
y Shells: Electrons determine size of the atom
y Outer-shell distribution: determines how element reacts
y … and the properties of combinations with others
y Isotopes: variants in terms of number of neutrons in nucleus
y C: most common = 12 amu ; C-14 = C-12 plus 2 neutrons
y Compounds vs. Mixtures: both made of 2+ atoms
y Compound = atoms react to form new substance
y Generally different from individual atoms!
y Na = explosive in water, Cl = toxic gas; NaCl = edible.
Atoms = building blocks of mass.
Atoms = building blocks of mass.
Combos = molecules, compounds, mixtures.
Combos = molecules, compounds, mixtures.
y Compounds vs. Mixtures: 2+ atoms
y Mixture = atoms do not react, stay
separate (Example: AIR)
78.00% N
21.00% O
0.04% CO2
0.003% Ne, He, methane, H, Kr
y Molecule = 2+ atoms bonded by a sharing of electrons
y Molecules together form unique substance (e.g., water, CO2)
y Crystals: NOT made of molecules: repeating pattern of atoms.
y Crystal atoms: held together by significant energy
y (all of it goes to building the structure… no excess.)
DNA molecule
NaCl
Crystal atoms: held together by significant energy = usable energy?
Atoms = building blocks of mass.
Where is all the antimatter?
antimatter?
y Antimatter: reacts with matter,
y Predicted, discovered (50s); now routinely produced
y Same mass, just oppositely charged.
y Anti-electrons (=positrons), antiprotons, antineutrons
y Observations: matter dominates antimatter. Why?
Answer:
Atoms = building blocks of mass.
Where is all the dark matter?
matter?
Atoms = building blocks of mass.
y “Dark matter”: unseen mass, source of gravitation in universe
y Observable universe: made of known elements!
y Makes up about
of the mass of the known universe!
y Atoms are mostly nothing.
y DM composition: cannot be observed, unknown elements
y EVERYTHING = only 100+ elements
y What is it? Currently being actively investigated!
y Combos = molecules, compounds, mixtures
y Why matter dominates antimatter; why dark
matter dominates observable matter = unsure