Transcript PPT
Atomic Structure Basic and Beyond What are the 3 major parts of an atom? Protons Electrons Neutrons Where is each located? Protons Protons= + and found in the nucleus. Discovered by Ernest Rutherford. Protons have a mass, we designate this mass as: 1 amu (atomic mass unit). Protons determine the atomic number and thus the identity of the substance. What experiment did Rutherford use to discover protons? Can protons be broken down? Experiments done in the late 1960's and early 1970's showed that protons are made from other particles called quarks. Quarks Quarks are sub, sub atomic particles that make up protons and neutrons They are found in pairs and have fractional charges Quarks Protons are made from two 'up' quarks and one 'down' quark. Neutrons Neutrons are uncharged particles found in the atomic nucleus. They have a mass of 1 amu Isotopes result when neutron number changes The decimals in the atomic mass are from the AVERAGE of the isotopes. Neutrons were discovered by James Chadwick in 1932. Why would a neutron be hard to discover? Isotopes Example: Can Neutrons Be Broken Down? • Experiments done in the late 1960's and early 1970's showed that neutrons are made from other particles called quarks. Neutrons are made from one 'up' quark and two 'down' quarks. The Nucleus The nucleus is the central part of an atom. It is composed of protons and neutrons. Unlike in a living cell, the nucleus of an atom is not a physical thing. It is the name for the area that holds the protons and neutrons. The nucleus contains most of an atom's mass. Why? Electrons Electrons= negatively charged particles that surround the atom's nucleus. The mass of an electron is so small that it is called “zero”. (It’s 1/1836 amu) Electrons determine chemical properties of the atom. Electrons are arranged in orbitals that are part of probability clouds. Who discovered electrons? What experiment was used? Why were they easy to discover? So subatomic particles are themselves made of smaller particles! • Subatomic particles composed of fast moving points of energy called quarks Quark Calculations (for protons and neutrons) Each proton is 2 up quarks and 1 down quark 2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1 Each neutron is 2 down quarks and 1 up quark 2(-1/3) + 2/3 = 0 What forces hold the atom together? Electromagnetic Strong Force likes repel, opposites attract (+ or -) interacts with hadrons or nucleons so the protons and neutrons binds them together works only at distances smaller than 1 quadrillionth of a meter!!! Weak Force works with quarks and leptons and decides how flavors change helps stabilize nuclei through beta decay shorter distances than the strong force! Gravity Since this binds matter together based on mass, we think this plays no role in atoms What is a quark, anyway? Fundamental particle which possesses electric charge and 'strong' charge. They combine in groups of two or three to form mesons and baryons The are held together by the strong force. There are several kinds of quarks Quarks come in six different species (physicists call them 'flavors') each flavor has a unique mass. So, are there other characteristics of quarks? The two lightest are 'up' and 'down' quarks They combine to form protons and neutrons. The heavier quarks aren't found in nature and have so far only been observed in particle accelerators. Can we get smaller? Fermions Bosons Leptons Hadrons And more So we can catagorize And get smaller But quarks are still the smallest for now Can things get even smaller? Higgs boson Neutrino And more are recently discovered sub sub sub particles! Looking at the new implications of these discoveries! Why are sub subatomic particles important? Predict properties such as nuclear decay Explain types of nuclear decay Help us to understand organization of matter Could lead to many things in the future: energy, new elements How are new particles discovered? How do accelerators work? Watch the following video • Standard model of Physics • https://www.youtube.com/watch?v=V0KjX sGRvoA