Bohr – Rutherford Atomic Model Neils Bohr improved Rutherford’s model by placing electrons in distinct energy levels or “shells” rather than an electron “cloud”

Bohr – Rutherford Atomic Model: Bohr & Rutherford combined their theories to create the current simplified atomic model The atom is made up of three sub-atomic particles: Protons Electrons Neutrons

The Atom: - + Proton Electron Neutron 1 amu nucleus outside nucleus Sub-Atomic Particle Charge Mass Location + 1 amu nucleus Proton outside nucleus - 1/2000 amu Electron Neutron none 1 amu nucleus

The Atom: electron neutron nucleus proton education.jlab.org/ qa/atom_model.html

Nucleus: Electrons: Contains protons & neutrons Overall positive charge (+) Contains nearly all mass (dense) Electrons: Located outside nucleus Easily moved, lost or gained Negative charge (-)

The Atom – Important Info: Since atoms are neutral, the number of protons (+) equals the number of electrons (-) Every atom has a symbol & two numbers associated with it. Ex. Atomic Number C 12 6 The number of protons The smaller number Mass Number The mass of an atom The number of protons & neutrons The bigger number

O Ex #1 For the following atom, state the… 8 16 i) mass number ii) atomic number iii) # of protons iv) # of electrons v) # of neutrons 16 O 16 8 8 8 8 16 – 8 = 8

Na Ex #2 For the following atom, state the… 11 23 i) mass number ii) atomic number iii) # of protons iv) # of electrons v) # of neutrons 23 11 11 Na 11 23 11 23 – 11 = 12

Ar Ex #3 For the following atom, state the… 18 40 i) mass number ii) atomic number iii) # of protons iv) # of electrons v) # of neutrons 40 18 18 Ar 18 40 18 40 – 18 = 22

Cu Ex #4 For the following atom, state the… 29 64 i) mass number ii) atomic number iii) # of protons iv) # of electrons v) # of neutrons 64 29 29 Cu 29 64 29 64 – 29 = 35

P Ex #5 For the following atom, which statement is TRUE? 15 31 A) The atomic number is 31. B) The atom has 15 neutrons. C) The atom has 16 electrons. D) The atom has 15 protons & 15 electrons. P 31

Ex #6 Given a neutral atom, which statement is TRUE? A) An atom always has the same number of electrons as neutrons. B) Electrons & neutrons are found in the nucleus. C) The atomic number states the number of neutrons. D) An atom has the same number of electrons as protons.

Key Points to Remember Atoms are made up of: Protons Electrons Neutrons Protons & Neutrons are located in the nucleus Electrons are located outside the nucleus

Key Points to Remember An atom’s atomic number is equal to the number of protons (smaller number) An atom is neutral, therefore the number of protons & electrons are equal An atom’s mass number is equal to the protons & neutrons together (bigger number)

Activities: Physical Science Worksheet #7 Once you’ve completed the worksheet, continue with the rest of the lesson

Electrons: Recall, in the Bohr-Rutherford atomic model, electrons are located outside the nucleus Electrons are organized into: Electron shells or Energy levels or Orbitals Be familiar with all the terms, especially the first two

Electrons: *Simplified – 3rd shell holds 18 electrons 4th shell holds 32 electrons Each electron shell differs in size & the number of electrons it can hold (capacity) Shows maximum # of electrons in each shell Electron Shell Capacity 1st 2 electrons 2nd 8 electrons 3rd 8 electrons* 4th 2 electrons* Shells can be partially filled or empty

Bohr – Rutherford Diagram: Is a picture of an atom, showing its protons, electrons & neutrons. Ex. Li 7 3 Protons = 3 First Electrons= 3 Neutrons= 4 Second 3 P+ 4 N0 2 e- 1 e- Third

F Ex #1 First Second Third 9 19 Draw a Bohr-Rutherford diagram for: Protons = 9 Electrons= 9 Neutrons= 10 9 P+ Second Third 10 N0 2 e- 7 e-

B Ex #2 First Second Third 5 11 Draw a Bohr-Rutherford diagram for: Protons = 5 Electrons= 5 Neutrons= 6 5 P+ Second Third 6 N0 2 e- 3 e-

Mg Ex #3 12 24 Draw a Bohr-Rutherford diagram for: Protons = 12 Electrons= 12 Neutrons= 12 12 P+ 12 N0 2 e- 8 e- 2 e-

K Ex #4 19 39 Draw a Bohr-Rutherford diagram for: Protons = 19 Electrons= 19 Neutrons= 20 19 P+ 20 N0 2 e- 8 e- 8 e- 1 e-

Ex #5 Which of the following diagrams best represents the Bohr-Rutherford model of… Be 9 4 A) C) 4 P+ 4 P+ 3 e- 2 e- 2 e- 5 N0 5 N0 2 e- B) 5 P+ 2 e- 2 e- 4 N0

Ex #6 Draw a Bohr-Rutherford diagram for each of the following atoms: P 31 15 N 14 7 Al 27 13 8 e- 7 P+ 8 e- 15 P+ 5 e- 13 P+ 7 N0 16 N0 5 e- 2 e- 14 N0 2 e- 2 e- 3 e-

The Neutron The Rutherford-Bohr model of the atom did not answer the question: “What holds the nucleus together given that it is made up of entirely of positive protons?”

The Neutron In 1932, James Chadwick discovered that a third sub-atomic particle called the neutron holds the protons in the nucleus together. Neutrons are located in the nucleus and have no charge…they are neutral.

Nucleus: Electrons: Contains protons & neutrons Overall positive charge (+) Contains nearly all mass (dense) Electrons: Located outside nucleus Easily moved, lost or gained Negative charge (-)

Find the number of Protons, Electrons & Neutrons Key Points to Remember Electrons are located outside the nucleus in electron shells In the… 1st shell – 2 electrons 2nd shell – 8 electrons 3rd shell – 8 electrons* 4th shell – 2 electrons* In Bohr-Rutherford diagrams: Place Protons & Neutrons in nucleus Place Electrons in appropriate shells First Find the number of Protons, Electrons & Neutrons

Activities: Physical Science Worksheet #8