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Atomic Concepts

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  1. Atomic Concepts How the building blocks of life work; and where they came from Brought to you by Erica Stevens

  2. Words to Know • Atom: the smallest particle of an element that has the chemical identity of that element • Electrons: Negatively charged particles outside of the nucleus • Protons: carry the positive charge of the nucleus • Neutrons: Have no electrical charge (neutral) and are also found in the nucleus

  3. Early Models of the Atom • J. J. Thomson used cathode rays to establish his “plum-pudding” model • Negative charges are distributed evenly throughout an atom’s positively charged interior. • Ernest Rutherford shot a beam of alpha particles at a piece of gold foil and most passed through; but some scattered • An atom is mostly empty space in which there is a small dense positive nucleus with electrons orbiting it.

  4. Ions 3+ F Al - • When an atom loses or gains one or more electrons it acquires a net electrical charge and is called an ion • A positively charged ion has more protons than electrons • A negatively charged ion has more electrons than protons • Net charge = #protons - #electrons • Mg2+has how many electrons?

  5. Isotopes 14 C • Atoms that have the same number of protons but different numbers of neutrons • Chemical characteristics of isotopes are basically the same • Mass is the big difference • Atomic mass on the periodic table is a weighted average mass based on natural abundance 37 Cl

  6. The Nucleus • Like charges repel each other; so how do all those protons make up the nucleus? • Strong Nuclear force is an attractive force that is strong enough to over come proton-proton repulsions and thus hold protons and neutrons together in the nucleus • There is a stable ratio of protons to neutrons which is not always 1:1 once the atomic number increases (more about that in nuclear chemistry)

  7. The Excited State • Niels Bohr decided that when electrons are given a specific amount of energy they can become excited and jump to a higher energy level • They quickly fall back down to the ground state and release this energy in the form of light

  8. And Finally……

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