CHMY 121IN 1st Edition Lecture 8 Review- Rutherford’s experimento Scattering of alpha particles to show there is a nucleus in an atomo Nucleus is slightly positive- Atomic Structure- Isotopes and Atomic Masso Elements of the same kind (same chemical symbol) can have a different number of neutrons as shown in the mass numbero The mass and abundance of the isotopes determine the atomic mass- Atomic Masso Actual weight is known as the Atomic Mass (measured in atomic mass units, amu) o We know that carbon-12 has 6 protons and 6 neutrons. The size of a proton and neutronare similar and if we want them to be 1 amu then the mass of 1 carbon atom must be 12amus- Chemical Periodicityo Mendeleev found that the properties repeated every 8 elements for the known 70 elements of his time This arrangement lead to the creation of the Periodic table – Vertical columns are groups Have 2 different numbering systems Have similar chemical reactivity Horizontal rows are periods Numbered 1-7These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Today’s Lecture- Element Arrangemento Metals – Shiny, bendable and conduct heat and electricity well o Non-metals – Dull, brittle and poor conductors of heat and electricity o Semi-metals or metalloids – Act as both a metal or non-metal for various properties – Semiconductors- Group Nameso Alkalio Alkaline Earth Metalso Chalcogenso Halogenso Noble Gases- Atomic Sizeo Reported as atomic radius (AR); units are Angstroms (Å, 10-10 m) or nmo • Size increases as you go down a groupo • Size decreases as you move left to right- Ionization Energyo Electrons are held to the nucleus through charge attraction o Pulling electron away requires energy o This is called the ionization energy- Accepting/ Donating Electron Ionso Atoms are electrically neutral (positiveo charge = negative charge) If this balance is off, the atom will have a charge and is called an ion This occurs when an electron is added or removed- Imperfection of Rutherford Modelo Rutherford’s model violated classical physics Scientists began to look at light given off by excited gases for clues When excessive energy is added to atoms and they are ionized, they emitenergy as light- What is Light?o Light behaves as a particleo Can count the number of light packets (known as photons) Light behaves as a waveo Moves at a characteristic wavelength/frequency.- Wavelengths- Colors and wavelengthso We can detect (with our eyes) light from roughly 400 to 700 nm Different wavelengths of light give different colors- Energy of Lighto The energy of light can be determined from its wavelengtho E = energy in Joules (J)o h = Planck’s constant (6.626 x 10-34 Js)o c = speed of light (3.00 x 108 m/s)o l = wavelength in meters (m)Announcements- Sign-up sheet disappeared Friday- – Available make up times areo 10-11 am in Wilson 1-125o 1-2 pm in Reid 104o 3-4 pm in Reid 202o Homework 2 due at 11 pm tonighto Exam 1 Review Session tonight (7-9pm) in- Gaines 101o – Bring questions and problems to work- • Check postings on D2L (answers to additional questions, tutorial on Study Area in Mastering Chemistry, constants and periodic table for
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