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Atomic Structure

Atomic Structure. What is an atom?. Atom: the smallest unit of matter that retains the identity of the substance Atoms are the “Building Blocks” of all matter – What does this mean?. Atomic Structure. Atoms are composed of 2 regions :

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Atomic Structure

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  1. Atomic Structure

  2. What is an atom? • Atom: the smallest unit of matter that retains the identity of the substance • Atoms are the “Building Blocks” of all matter – What does this mean?

  3. Atomic Structure • Atoms are composed of 2 regions: • Nucleus: the center of the atom that contains the mass of the atom • Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Nucleus Electron Cloud

  4. What’s in the Nucleus? • The nucleus contains 2 of the 3 subatomic particles (What does subatomic mean?) • Protons: positively charged subatomic particles (+) • Neutrons: neutrally charged subatomic particles (Ø)

  5. What’s in the Electron Cloud? • The 3rd subatomic particle resides outside of the nucleus in the electron cloud • Electron: the subatomic particle with a negative charge and relatively no mass • (-)

  6. How do these particles interact? • Protons and neutrons live compacted in the tiny positively charged nucleus accounting for most of the mass of the atom. They are held together by the strong force. (Each mass = 1amu) • The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus (mass = 0 amu)

  7. How do the subatomic particles balance each other? • In an atom: • The protons = the electrons • If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral • The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

  8. How do we know the number of subatomic particles in an atom? • Atomic number: this number indicates the number of protons (and electrons)in an atom • Ex: Hydrogen’s atomic number is 1 • So hydrogen has 1 proton & 1 electron • Ex: Carbon’s atomic number is 6 • So carbon has 6 protons & 6 protons **The number of protons identifies the atom. The # of protons = # of electrons Ex. 2 protons = He, 29 protons = Cu

  9. How do we know the number of subatomic particles in an atom? • Mass number: the number of protons and neutrons in the nucleus • Ex: Lithium has a mass of 7. So the sum of protons and neutrons would be 7. • # of neutrons = mass # - atomic # OR • Mass # - Atomic # = # of neutrons

  10. Determining the number of protons and neutrons • C has a mass number of 12 and an atomic number of 6 • How many protons does Carbon have? • How many electrons does Carbon have? • How many neutrons? • Ne has a mass number of 20 and an atomic number of 10 • Protons ? Electrons ? • Neutrons ?

  11. What about the electrons? • The electrons are equal to the number of protons • So e- = p = atomic # • Ex: He has a mass # of 4 and an atomic # of 2 • p+ = 2 • no = 2 • e- =2

  12. Determine the number of subatomic particles in the following: • Cl has a mass # of 35 and an atomic # of 17 • p+ = 17, no = 18, e- = 17 • K has a mass # of 39 and an atomic # of 19 • P+ = 19, no = 20 e- = 19

  13. How exactly are the particles arranged? • Bohr Model of the atom: All of the protons and the neutrons The 3rd ring can hold up to 18 e- The 1st ring can hold up to 2 e- The 4th ring and any after can hold up to 32 e- The 2nd ring can hold up to 8 e-

  14. What does boron look like? Mass # = 11 atomic # = 5 p+ = 5 no = 6 e- = 5 5 p and 6 n live in the nucleus

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