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Getting inside the atom part 2
 

Getting inside the atom part 2

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    Getting inside the atom part 2 Getting inside the atom part 2 Presentation Transcript

    • Figure 3.9: A nuclear atom viewed in cross section.
    • The Nucleus• The nucleus forms the central dense core of the atom (ca. 10-13 cm diameter). It consists of particles referred to as nucleons. There are two types of nucleons: protons and neutrons.• A nucleus consists of at least one proton.• Most nuclei also consist of one or more neutrons. n p p n n p
    • Atomic Structure The # of protons determine the type of element it is and it’s chemical/physical characteristics There are three characteristics that can be discussed about each particle – Charge – Mass – Location
    • Atomic Structure Protons have a positive charge (+), an atomic mass of 1.0073 and are found in the nucleus Electrons have a negative charge (-), an atomic mass of 0.000549 and are found in the electron cloud Neutrons have no charge (ø), an atomic mass of 1.0087 and are found in the nucleus
    • Properties of Subatomic Particles
    • The Structure of the Atom, continuedSurrounding the nucleus is a region occupied by negatively charged particles called electrons.Protons, neutrons, and electrons are often referred to as subatomic particles.
    • Composition of the Atomic Nucleus Except for the nucleus of the simplest type of hydrogen atom, all atomic nuclei are made of protons and neutrons. A proton has a positive charge equal in magnitude to the negative charge of an electron. Atoms are electrically neutral because they contain equal numbers of protons and electrons. A neutron is electrically neutral.
    • Composition of the Atomic Nucleus, continued The nuclei of atoms of different elements differ in their number of protons and therefore in the amount of positive charge they possess. Thus, the number of protons determines that atom’s identity.
    • Composition of the Atomic Nucleus, continued Forces in the Nucleus When two protons are extremely close to each other, there is a strong attraction between them.  A similar attraction exists when neutrons are very close to each other or when protons and neutrons are very close together.  The short-range proton-neutron, proton-proton, and neutron- neutron forces that hold the nuclear particles together are referred to as nuclear forces.
    • Atomic Number Atoms of different elements have different numbers of protons. Atoms of the same element all have the same number of protons. The atomic number (Z) of an element is the number of protons of each atom of that element.
    • Atomic Number
    • Mass Number The mass number is the total number of protons and neutrons that make up the nucleus of an isotope.
    • Mass Number
    • Isotopes Isotopes are atoms of the same element that have different masses. The isotopes of a particular element all have the same number of protons and electrons but different numbers of neutrons. Most of the elements consist of mixtures of isotopes.
    • Figure 3.10: Two isotopes of sodium.
    • Designating Isotopes Hyphen notation: The mass number is written with a hyphen after the name of the element. uranium-235 Nuclear symbol: The superscript indicates the mass number and the subscript indicates the atomic number. 235 92 U
    • Designating Isotopes, continued The number of neutrons is found by subtracting the atomic number from the mass number. mass number − atomic number = number of neutrons 235 (protons + neutrons) − 92 protons = 143 neutrons Nuclide is a general term for a specific isotope of an element.
    • Designating Isotopes, continuedSample Problem AHow many protons, electrons, and neutrons are there in an atom ofchlorine-37?
    • Designating Isotopes, continued Sample Problem A Solution Unknown: numbers of protons, electrons, and neutronsGiven: name and mass number of chlorine-37 Solution: atomic number = number of protons = number of electrons mass number = number of neutrons + number of protons
    • Designating Isotopes, continued Sample Problem A Solution, continuedmass number of chlorine-37 − atomic number of chlorine =number of neutrons in chlorine-37 mass number − atomic number = 37 (protons plus neutrons) − 17 protons = 20 neutrons An atom of chlorine-37 is made up of 17 electrons, 17 protons, and 20 neutrons.
    • Isotopes Practice List the number or Protons, Neutrons, and Electrons for each isotope. Mg2512 Al2713200 Hg80 Fe5726
    • Review and Terms There are different names given to different arrangements of protons, neutrons and electrons A nuclide is an atom that has a specific combination of neutrons and protons (i.e. U-238) Ions – are atoms which have either a positive or negative charge (+ or -) Isotopes are atoms with different #’s of neutrons
    • Atomic Structure Atomic # - is the number of protons in the nucleus of an atom, it is also how we find elements on a periodic table ( Z ) The Neutron number is given as ( N ) Atomic Mass – is the number of protons and neutrons found in an atom ( A ) – 1 amu =1/12 mass of C-12 99.99% of the mass of an atom is found in the nucleus
    • Describing a Nuclide A nuclide can be described by specifying:1. The number of protons. ( Z )2. The number of neutrons ( N )3. The total number of protons and neutrons. Also known as the atomic mass ( A ) – A=Z+N
    • Describing a Nuclide Atomic Mass A ZM Symbol for the chemical Atomic Number element For simplicity, it is more common to ignore the atomic number and follow the symbol for the element with the mass number M-A
    • Symbolizing a NuclideExamples: 12 6 protons and 6 neutrons, referred to as C carbon twelve, also symbolized C-12 6 13 6 protons and 7 neutrons, referred to as C carbon thirteen, also symbolized C-13 6 14 6 protons and 8 neutrons, referred to as C carbon fourteen, also symbolized C-14 6