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RAD 354 Chapt 3 Structure of Matter The atom is the smallest part of an element that has all the properties of the element – 112 elements have been identified.

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Presentation on theme: "RAD 354 Chapt 3 Structure of Matter The atom is the smallest part of an element that has all the properties of the element – 112 elements have been identified."— Presentation transcript:

1 RAD 354 Chapt 3 Structure of Matter The atom is the smallest part of an element that has all the properties of the element – 112 elements have been identified 92 are natural 20 were artificially produced

2 Interesting dates - info 1808 John Dalton classified elements according to atomic mass values Mendeleev first suggested the periodic table with 8 groupings – Atomic number (Z#)= NUMBER OF PROTONS – Atomic MASS # = elemental mass (A) AND neutrons

3 Nuclear model of the atom 1911 Ernest Rutherford introduced the nuclear model of the atom 1913 Niels Bohr improved on Rutherford’s The “mini solar system” model is now know as the Rutherford – Bohr model of the atom

4 Molecules Atoms of various elements may combine to forms moledules – Sodium (Na) + chlorine (CL) = sodium chloride (NaCL) = table salt

5 Chemical Compound Is a NEW substance that is formed when two or more atoms of different elements combine – Covalent bond – sharing electrons in outer orbital shells – Ionic bonding – atoms attracted to each other because of opposite charges Smallest particle of an element is an atom Smallest particle of a compound is a molecule

6 Atoms Three main parts: – Electrons – Protons – Neutrons Mass of an atom is expressed in atomic mass units (AMU’s) {1/2 mass of a carbon 12 atom} -AMU’s are always rounded numbers!

7 Electron “shells” /Orbitrons Shells are lettered K,L,M,N – etc from the nucleus outward (also numbered 1,2,3,4,5 from the nucleus outward). Max POTENTIAL number of electrons in any shell 2n 2 The number of electrons in the outer most shell tells which GROUP and PERIOD it exists in the periodic table

8 Varied #’s of mass# & atomic# Isotope = same # of protons but different # of neutrons Isobar = different # of protons and neutrons BUT same TOTAL number of nucleons Isotones = same # of neutrons BUT different # of protons Isomer = same atomic number and same atomic mass number- BUT exist at different energy states (varied nuclear arrangements)

9 Radioactivity Can be emission of alpha, beta or gamma Radioactive HALF LIFE = time required for a quantity of radioactivity to be reduced (decay) to ½ of it’s original value. NOTE: it will have the same specific energy constant – BUT only half the number of decays

10 Particulate vs electromagnetic Which of alpha, beta and gamma are particulate? Which is/are electromagnetic?

11 354 Chapt 4 Electromagnetic Energy Photons – No mass/charge – Have velocity, frequency, wavelength and amplitude – Follow the “duality therory” – Travel in discrete bundles of energy called (Quantum”

12 Velocity is the speed of light 3 X cm/sec OR 3 X 10 8 m/sec Photon is the smallest quantity of any type e/m radiation Photons have BOTH electric (A/C) and magnetic qualities Travel as sine waves

13 Units of E/M concern Amplitude = height of the sine wave Frequency (f) = length of successive points in the sine wave/cm – As f increases, so does energy (energy is DIRECTLY PROPORTIONAL to frequency) As velocity decreases, so does frequency Velocity = frequency X wavelength – V= F X ƛ

14 Electromagnetic Spectrum 3 ranges: visible light, RF, x-ray – All travel the speed of light, but may have diff. frequency and wavelength – Visible light is I’d by it’s wavelength, RF by it’s frequency and x-rays by energy – Radiation may be ionizing or non-ionizing Non may be reflected as well as absorbed Ionizing cannot be reflected BUT can be absorbed/partially absorbed and scattered


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