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Chapter 4. The Atom – Part 2. Lord Ernest Rutherford (1871 – 1937). Discovered the nucleus of the atom. Pioneered the orbital theory of the atom. Rutherford’s Gold Foil Experiment. Rutherford’s Gold Foil Experiment. Rutherford’s Nuclear Model of the Atom.
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Chapter 4 The Atom – Part 2
Lord Ernest Rutherford (1871 – 1937) • Discovered the nucleus of the atom. • Pioneered the orbital theory of the atom.
Rutherford’s Nuclear Model of the Atom • The nucleus is very small, dense, and positively charged. • Electrons surround the nucleus. • Most of the atom is empty space
The number of protons in the nucleus of the atom (atomic number = Z) determines the atoms identity Gold Atom Lead Atom
Mass Number • The sum of the protons and neutrons in the nucleus of an atom.
Carbon - 12 • This is the symbol for the isotope carbon-12. • Atomic number is 6. • Mass number is 12.
Isotopes • Isotopes are different types of atoms of a chemical element, having the same number of protons in the nucleus, but having different numbers of neutrons in the nucleus. • Isotopes therefore have the same atomic number but different mass numbers. • There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms. • Isotopes of a single element possess almost identical properties.
Carbon - 12 • Write the symbols for carbon-13 and carbon-14.
Atomic Mass • The atomic mass of carbon is 12.01 amu. • Atomic mass is the average mass of all the isotopes of an atom. It takes into account the different isotopes of an element and their relative abundance.
Common Uses of Isotopes • Isotope Analysis • Radiometric Dating • Nuclear Medicine: • Magnetic Resonance Imaging (MRI) • Positron Emission Tomography (PET scans)
Nuclear Medicine refers to imaging techniques that use radioactive isotopes to detect and treat disease. Magnetic resonance imaging (MRI) and positron emission tomography (PET scans) are examples.
An atom of vanadium contains 23 electrons. How many protons does it contain? 23 p+
An atom of silver contains 47 protons. What is its atomic number? 47
An “atom” of sodium contains 11 electrons. What is its atomic number? 11
How many electrons, protons and neutrons are in an atom of actinium with a mass number of 221? 89p+ 89e- 132n0
How many electrons, protons and neutrons are in an atom of rhodium-105? 45p+ 45e- 60n0
Homework • Chapter 4 Worksheet 1 (due Monday)