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Electrons. Ch.17 Sec.1. Niels Bohr. ( 1885-1962) Worked w/ Rutherford Agreed that atom had nucleus surrounded by large volume of space. 4.3 Modern Atomic Theory. Bohr’s Model : describes the arrangement of electrons in an atom
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Electrons Ch.17 Sec.1
Niels Bohr • (1885-1962) • Worked w/ Rutherford • Agreed that atom had nucleus surrounded by large volume of space
4.3 Modern Atomic Theory • Bohr’s Model: describes the arrangement of electrons in an atom • The electrons move in spherical orbits at fixed distances from the nucleus • Electrons are arranged in Energy Levels and only a certain number of electrons may occupy each energy level
How to Draw Atoms • Bohr Model - electrons move around the nucleus in orbits or energy levels • Like planets around sun
Energy Levels • Different levels have different energies • Can lose or gain energy and change levels • Levels closest to nucleus are lowest energy (less likely to be used in bonding)
Energy Levels • Electrons can move from one energy level to another when an atom loses or gains energy • All atoms have 2 electrons in their 1st energy level (level closest to the nucleus) • 2nd level = 8 • The levels closest to the nucleus has the strongest attraction or bonds • The last energy level of any atom has a maximum of 8 electrons
How To Draw Atoms • Many energy levels: • 1st -max of 2 e- • 2nd -max of 8 e- • 3rd - max of 18 e- • Must fill up in order
Valence Electrons • Electrons in outermost shell are called valence electrons • Ex: Carbon has 4 valence electrons, but 6 total electrons
Modern Atomic Model • Today use electron cloud model • Electron cloud shows most probable location of e- • Cloud is thicker where e- more likely to be • Like ceiling fan or propeller on plane