1. Bohr’s Atomic Model

2. In 1913, Neils Bohr, a Dane, proposed his model of the atom. It was a modification of the Rutherford model. Bohr however put the electrons in certain circular orbits called shells or principal energy levels (PEL’s). + 1 st shell (2 electrons max.) 2 nd shell (8 electrons max.) 3 rd shell (18 electrons max.) Nucleus Empty space The “planetary” model

3. Protons and neutrons are found in the nucleus. Electrons orbit the nucleus in various shells. Everything else is empty space. + 1 st shell (2 electrons max.) 2 nd shell (8 electrons max.) 3 rd shell (18 electrons max.) Nucleus Empty space The “planetary” model Bohr’s Atomic Model

4. Q:What are the Bohr models for the neutral atoms of the three isotopes of hydrogen? A:Step-1 Draw a box to represent the nucleus. Step-2 Determine the number of protons and neutrons and place them in the nucleus. Step-3 Draw one circle around the nucleus to represent the electron shell and then place the one electron in the shell. H-1H-2H-3 1p 0n 1p 1n 1p 2n e-e- e-e- e-e- Bohr’s Atomic Model

5. Q:What are the Bohr models for the neutral atoms of the two isotopes of carbon? A:Step-1 Draw a box to represent the nucleus. Step-2 Determine the number of protons and neutrons and place them in the nucleus. Step-3 Draw two circles around the nucleus to represent the electron shells and then place the six electron in the shells as indicated by the electron configuration. C-12C-14 6p 6n 6p 8n e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Bohr’s Atomic Model

6. Q:What are the Bohr models for the neutral atom 27 Al and the ion 23 Na 1+ ? A:Step-1 Draw a box to represent the nucleus. Step-2 Determine the number of protons and neutrons and place them in the nucleus. Step-3 As indicated by the electron configuration, draw arcs to represent the electron shells and place the electron on them. 27 Al 23 Na 1+ 13p 14n 11p 12n 2e - 8e - 3e - 2e - 8e - 0e - Bohr’s Atomic Model

7. Q:What are the Bohr models for the ion 37 Cl 1- and the neutral atom of calcium-42? A:Step-1 Draw a box to represent the nucleus. Step-2 Determine the number of protons and neutrons and place them in the nucleus. Step-3 As indicated by the electron configuration, draw arcs to represent the electron shells and place the electron on them. 37 Cl 1- Calcium-42 17p 20n 20p 22n 2e - 8e - 2e - 8e - 2e - Bohr’s Atomic Model

8. The last shell holding electrons is called the valence. Electrons in the last shell are called valence electrons. Q: How many valence electron are there in 37 Cl 1- ? A: 8 Q: Which shell in a neutral atom of calcium-42 is the valence? A: 4 th 37 Cl 1- 17p 20n 2e - 8e - Calcium-42 20p 22n 2e - 8e - 2e - Bohr’s Atomic Model