Atoms

Dalton’s Atomic Theory 1) All elements are composed of tiny individual particles called ______________. _________________ = A pure substance containing __________ of atom. All of the substances listed on the periodic table are elements (K, O, Br, C, etc.). 2) Atoms of the same element are ______________. Atoms of the same element have the same number of protons, neutrons, and electrons.

Dalton’s Atomic Theory 3) Atoms can mix together or chemically combine with one another in simple, whole-number ratios to form molecules and compounds. Molecule – A combination of ____________________________that are chemically bound to one another. (ex: H20, Br2, O2) Compound – A molecule containing two or more ________________ __________________ that are chemically bound to one another. (ex: H20, CO2, C6H1206) ie: All compounds are molecules, but not all molecules are compounds.

Compound or Molecule? Carbon Monoxide (CO) Liquid Bromine (Br2) Hydrochloric Acid (HCl) Chlorine Gas (Cl2)

Atomic Structure Nucleus Protons – Neutrons – Orbitals

Subatomic Particles Protons and electrons have _________ and _______________ charges. Protons and neutrons have ____________ masses (nearly), while electrons are 2,000x _______________ in mass.

History of the Atom As we’ve discussed, no one has “seen” an atom so it’s structure is theoretical. We’ll walk through how the theory of the atom has changed over time based on different lab evidence.

Early Atomic Models – Plum Pudding Anyone? Cathode Ray: - First evidence that of ____________________ charged particles existing. - If matter has (-) particles in it, but isn’t negative overall, there must be (_____) charge present to balance it out!

Plum-Pudding Model Negatively charged particles, spread out through a positively charged sphere

Advances in the Atomic Model: Rutherford’s Atom Gold Foil Experiment: ____________ particles (2p/2n) are “Red Rovered” at a thin piece of gold foil, just a couple _____________ thick. +2 +2 +2

Gold Foil Experiment Hypothesis If the charges in an atom are spread out (Plum-Pudding), the positively charged alpha particles should be able to ______________ __________________________ Gold-Foil Experiment

Gold Foil Experiment Results The fact that some particles _______________ shows there must be a concentrated region of __________________ charge in the atom, with negative particles found __________________________. Almost all of the particles ____________________________, showing the positive area was a very, very small core (____________) and almost all of the atom was a less dense negative area (___________________)

Rutherford Model ___________________ don’t follow a defined, circular path around the nucleus. Electrons can be found anywhere within a defined “_____________” region. The “cloud” is a graphical depiction of the area around the nucleus where an e- is ___________ ____________ at any given moment.

Lab Support for Rutherford’s Model Mapping Electron Clouds

Bohr Model Electrons follow defined pathways around the nucleus called ________ _____________. They can jump up to higher energy levels if they absorb _______________ = __________________ When they fall back down to their original energy level, they release the energy back out as a ___________ wave = ___________________

Lab Support for Bohr’s Model Light Emission: electron transitions between the same energy levels always produce the same _____________ photon (light) emission. Emission Animation

What does Bohr’s experiment show us? Stay with me here… Different ____________ of visible light waves have unique __________________ (ex: red light = 700nm, blue = 475nm) The __________ of a light wave is dependent on its ___________________ (we’ll talk about the equation later) Short Wavelength = Long Wavelength = Therefore, a wave’s energy is directly related to it’s ___________ (wavelength) Blue = Red =

Quantized Energy Levels If we get the same __________ every time an electron drops down between the same _________ ____________, the levels must be a specific amount of _____________ apart!

Building Elements As we build atoms (add protons/neutrons/electrons) notice what happens to the atoms’ 1) 2) 3) http://phet.colorado.edu/en/simulation/build-an-atom

Building Atoms Summary Changing the number of ______________ was the only thing that changed the _______________. The number of protons in the _________ determines the element Changing the __________ of protons to neutrons influences the ________________ of the nucleus. Changing the ratio of protons and electrons causes an overall ______________ to form on the atom. More protons → More electrons →

Why is it that certain combinations of nucleons are stable in a nucleus while others are not? A complete answer to this question cannot yet be given, largely because the exact nature of the forces holding the nucleons together is still only partially understood The ratio between the ______________ and ______________ appears critical.

Columns = ___________ (1-18) Rows = _____________ (1-7) Know Your Group Names! - Alkali Metals - P-block Metals/Non-metals - Halogens - Semi-Metals - Alkaline Earth Metals - Transition Metals - Noble Gases

How to Read the Periodic Table Atomic Number : Element Symbol: Atomic Mass: