Sep 29 11:29 AM Vocabulary QUIZ: 1. The total number of particles in the nucleus 2. 1 / 12 th of the mass of a carbon atom 3. The weighted average mass of all the isotopes of a particular element 4. A helium nucleus is the same as this, two protons and two neutrons 5. An extra negative electron is the same as this 6. The rays and particles emitted by uranium 7. Unstable atoms under go this 8. I'm "positive" this particle is in the nucleus 9. This particle is like Switzerland 10. Two atoms differ only in mass number but not atomic number, they must be. Sep 11 9:25 AM 1
Atom Models Scientists wanted to understand how the atom looked It was known that matter was neutral It was known that matter had mass They used these to ideas to come up with their models, however science changed as technology developed Video Sep 11 12:31 PM History of Atomic Theory ΕΡΛΨ ΓΡΣΣΚ ΘΟΤ Democritus and Leucippus- Greek philosophers who came up with the concept of an atom from the Greek word atomos which means indivisible. OR Aristotle - Famous philosopher who believed that all substances were made of 4 elements: Fire Hot, Air light, Earth - cool, heavy, and Water wet. Blend these in different proportions to get all substances Who Was Right? Sep 10 9:05 AM 2
notes 2015.notebook Medieval Times In medieval times, alchemists began experimentation. They are known for trying to change lead to gold. Out of this practice emerged the modern chemists, the first being Sir Robert Boyle in the 1600s. He was the first to do actual chemical experiments. He helped end the idea of the four elements. Sep 10 12:20 PM Late 1700 s - John Dalton, an English school teacher, summarized results of his experiments and those of other scientists. His conclusions led to the first scientific theory of the atom. What is a scientific theory? Sep 10 1:04 PM 3
Dalton s Atomic Theory 1. All matter is made of tiny indivisible particles called atoms. 2. Atoms of the same element are identical, those of different elements are different. 3. Atoms of different elements combine in whole number ratios to form compounds. 4. Chemical reactions involve the rearrangement of atoms. No new atoms are created nor destroyed. Sep 10 1:07 PM MODERN VIEWS of the ATOM Atom: The smallest particle of an element that retains the properties of the element. Most atoms consists of three particles: proton neutron electron Sep 10 1:10 PM 4
History of the Atom Plum Pudding model: (J. J. Thomson in 1897) Spherically shaped Electrons (negatively charged) positioned throughout it like chocolate chips in a cookie The sphere was a positively charged mass, like the cookie dough Idea did not last long Video Sep 5 8:04 PM History of the Atom Ernest Rutherford (1911) Shot a beam of radiation particles at a thin sheet of gold He expected the particles to go straight through if the atom was based off the Plum Pudding Model. Particles should only alter course if they hit an electron in the atom Sep 5 8:58 PM 5
History of the Atom Ernest Rutherford (1911) The atom was made up of mostly empty space where the electrons moved The positive charge of the atom was within the center of the atom: The nucleus a small dense positively charged space at the center of an atom Electrons are held within the atom due to the attraction of the nucleus The diameter of the atom was calculated to be 10,000 times the diameter of the nucleus (comparison: if the diameter of the nucleus was the size of my desk (1.34 m), how big would the diameter of the atom be?) in miles? 0.62 miles=1km Sep 6 9:04 AM History of the Atom James Chadwick Video Sep 6 9:11 AM 6
History of the Atom The Nucleus contains protons and neutrons, containing 99.97% of the atoms mass Protons are a positively charged subatomic particle Neutrons are neutrally charged subatomic particle Nucleus is surrounded by negatively charged electrons, with negligible mass Protons and electrons are attracted to each other Atoms are mostly empty space Video Sep 6 9:11 AM The Atom 6 C Carbon 12.011 Atomic Number Element Symbol Element Name Atomic Mass Sep 7 8:13 AM 7
The Atom Atomic Number 6 C Carbon 12.011 This tells you how many protons are in the atom (ALWAYS!!!) The # of protons is the DNA of the atom, it makes it that element This also tells you how many electrons there are in a neutral atom (remember protons are positive and electrons are negative Sep 7 8:13 AM The Atom 6 C Carbon 12.011 Atomic Mass Measured in Atomic Mass Units (AMUs) Atomic mass number of any one atom = # Protons + # Neutrons Remember Electrons mass is Negligible 12 amu 6 protons = 6 neutrons Round the mass to a whole number Sep 7 9:11 AM 8
The Atom 6 C Carbon 12.011 Average Atomic Mass (Why is this number not a whole number?) This is the weighted sum of all the atomic masses possible for this element Since protons do not EVER change, and electrons mass is negligible, the only thing that can change the mass is a change in Neutrons Isotopes: Atoms with the same number of protons but different number of Neutrons Sep 7 9:11 AM Oct 8 1:53 PM 9
Writing isotopes Uranium 238 mass number U 238 92 \ atomic # Sep 13 10:21 AM Isotopes amu oxygen 18 9 3 Li Bromine 80 p n e - 139 56 199 79 Ba Au Sep 13 10:25 AM 10
Oct 8 2:10 PM Isotopes amu Nitrogen 15 41 20 Ca p n e - Radon 222 100 42 109 47 Mo Ag Sep 13 10:25 AM 11
The Atom Atomic Mass Calculation [% of Mass 1 x (Mass 1)] + [% of Mass 2 x (Mass 2)] +... Copper has two isotopes: 69.2% of all copper has a mass of 63 amus and 30.8% of all copper has a mass of 65 amus. What is copper's atomic mass? Sep 7 9:22 AM Warm up 10/6/2015 Tin (Sn) has four different isotopes. What is the average atomic mass of a sample of Tin that has 55.0% of its isotopes having 118 amus, 19.0% having 119 amus, 20.0% having 120 amus, and 6.0% having 121 amus? Oct 2 8:45 AM 12
Radioactivity Fission Fusion + + Oct 13 1:39 PM Splitting the Atom Radioactive decay occurs when an atom undergoes a nuclear reaction. The nucleus breaks apart into a more stable structure. When this happens particles and energy are released. These particles and energy are called radiation. Three types of radiation: alpha beta gamma Sep 11 1:14 PM 13
Alpha Radiation Alpha radiation is a very weak form of radiation. It can easily be stopped by human skin or paper. In alpha radiation, alpha particles are given off. An alpha particle contains two protons and two neutrons (a helium nucleus). It carries a +2 charge. 226 88 Ra 222 86Rn + α Sep 12 10:14 AM Alpha Radiation Niobium 94 undergoes alpha decay Barium 138 undergoes alpha decay Lead 209 undergoes alpha decay Oct 13 2:01 PM 14
Beta Radiation Beta radiation is a stronger form of radiation. It can be stopped by aluminum foil or an inch of acrylic. In beta radiation, beta particles are given off. A beta particle is a particle with a -1 charge 14 6 C 14 7N + β - + neutrino How does this happen? Sep 12 9:07 AM Beta radiation (cont.) A neutron decomposes into a positive proton and releases the negative portion as a negatively charged particle and the extra energy as a neutrino 14 6 C 14 7N + β - + neutrino Sep 12 11:08 AM 15
Beta Radiation Carbon 14 undergoes beta decay Potassium 40 undergoes beta decay Strontium 88 undergoes beta decay Oct 13 2:10 PM Gamma radiation Gamma radiation is the strongest form of radiation. It is deadly to life. It can be stopped by an inch of lead or a meter of concrete. It will not turn you into the Hulk. Sep 12 11:13 AM 16
Gamma radiation In gamma radiation, a very unstable nucleus has too much energy. To become stable, the nucleus releases the energy in the form of gamma rays and also other particles (beta, alpha, and/or neutrons) Sep 13 9:28 AM Gamma radiation Rubidium 86 undergoes only gamma decay Rubidium 86 undergoes gamma decay and the releases a neutron Rubidium 86 undergoes gamma and alpha decay Rubidium 86 undergoes gamma and beta decay Oct 13 2:18 PM 17
Practice 1. 54 Mn undergoes beta decay. What is the final product? 25 2. Antimony 122 goes through alpha decay and then a beta decay. What is produced? 3. What new element is created by the beta decay of polonium 210? 4. 128 If 53I was produced by two beta decays, what was the original element? Oct 14 12:28 PM Oct 6 9:12 AM 18