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Download Atoms! - Holtmeyerhouse
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Democratis – the founder of atoms Early Greek-early philosopher who came up with the term atom. Described the building block of all substances 2 Laws govern these atoms, the Law of definite proportion, and the Law of multiple proportions Definite and Multiple proportion Definite- says that a compound has a fixed ratio of atoms H20- H weighs 2 for every 16 O Same two atoms can combine in multiple ways PbO, PbO2 FeO, Fe2 O3 Carbon dioxide, carbon monoxide If H weighs 4, the O has to weigh 32, Dalton and his law Atoms are the smallest set of matter Atoms of same element are the same, atoms of different elements are different Atoms can’t be created or destroyed Atoms combine into compounds In compounds, atoms are always in whole number ratios Modern atomic theory, was Dalton correct? Atoms are the smallest set of matter Atoms of same element are the same, atoms of different elements are different Atoms can’t be created or destroyed Atoms combine into compounds In compounds, atoms are always in whole number ratios 1 protons, neutrons and electrons, quarks, lepetons, Change mass numbers, changes properties, called Isotopes!!! Fission, Fusion Yes Yes Atoms! What they are made of Electrons – the negative part of atoms, roam around the exterior of atoms. Mass negligible. Weigh 1/1832th of the atom. Nucleus Houses protons. Positive charge, very heavy, make up a lot of the mass. Neutrons- have no charge, but mass = to protons. Other good info If the atom were size of a football field , the nucleus would be a dime in the center. ( it would weigh more than a semi truck) Rest of field would be space for electrons, which would weigh no more than a fly. In an atom, the number of protons is = to the number of electrons. The periodic table and how it helps Atomic number is the number of protons. This defines an element Atomic weight- the weight of protons+ neutrons in atomic mass units Round that to a whole number, it counts protons + neutrons. Try some, write p+, N, and e- for the following C, H, N, O, Ne, He, B, Na What if the atom is active? Atoms do gain or lose electrons. Called an ION!!!!!! Has a positive or negative charge. Na with 11 p+ and 10 e-. Na+1 S have 16 p+ and 18 e-. S -2 How many electrons does Mg +2 have? How about O-2? Does their proton number change? Their mass? What happens if the neutron number is different? All atoms come in different varieties. They have the same number of protons, but the neutron number changes. That means the mass number changes and so do the properties. Usually the change makes the less common varieties radioactive Isotope is the name for atoms with same atomic number but different mass number Isotopes The atomic mass on the periodic table is an average of all the types of that elements, with weight given for how much of each there is Usually in here we are referring to the most common, so the numbers off the periodic table are fine. •If you want to refer to a specific isotope, there are 2 ways to write it. •Isotope notation. Use the name of the element- mass number ( rounded atomic mass •You try some •Sodium that weighs 22.99 • Calcium that weighs 41.33 Nuclear notation This looks like the block of the periodic table. Use mass number over atomic number 55 26 Fe 84 or 36 Kr You try, write the isotope that is silver with a mass of 109, and Nickel that has 28 protons and 32 neutrons. Nuclear reactions!!! Nuclear reactions- change in nucleus. Most atoms have stable nucleus that doesn’t change, There is a force in the nucleus that ties protons and neutrons together. but a few atoms are radioactive, which means their nucleus’s do change, and give off radiation. . Types of atoms that are radioactive Neutrons have no force, so they do not repel, they are like the glue helping hold together. When get too many protons ( above 83) not enough neutrons to hold. So all elements above 83 are radioactive. (state some) Also isotopes of stable atoms that have too many neutrons makes an atom unstable! Hydrogen –2 and Hydrogen –3, also Carbon -14 What is radioactivity? Radioactivity- first discovered when uranium sample was put on photographic film Radioactivity is the spontaneous emission of radiation from an element. Not necessarily dangerous! There are 3 types 1st 2 types of radioactivity- not dangerous Alpha particles have double the charge of an electron with opposite charge so +2. Very low penetrating power. Can’t hurt you!!!! Lots of this given off all the time all over the place!! Stopped by paper they have 2p and 2n. just like He-4. write with an “” Can also write 4/2 He or 4/2 Beta particles write with a “” 0/-1 are high speed electrons -1 charge stronger penetrating, stopped by heavy clothing can penetrate light clothing or skin. The dangerous type of radiation! Gamma radiation Write “ ” is similar to X rays, and has no charge/ particles. High, have to be stopped by lead. How to write nuclear equations The proton and neutron numbers must add up, so write it like a math equation Try Xe + alpha U 238 = alpha + __________ Th233 = beta + ___________