BohrRutherford Diagrams THE BOHRRUTHERFORD MODEL n n In

Bohr-Rutherford Diagrams

THE BOHR-RUTHERFORD MODEL n n In the early 1900’s, two European scientists, Neils Bohr and Ernst Rutherford, made major discoveries about the atom. They came up with the following ideas through careful experimentation:

1. Electrons move in orbits around the atom’s nucleus just like planets move in orbits around the Sun. 2. The electron orbits are at specific distances away from the nucleus. 3. Electrons can move from one orbit to another, but they cannot stay in the spaces between orbits.

4. The first orbit can hold a maximum of 2 electrons. The second and third orbit can hold a maximum of 8 electrons. 5. Electrons are more stable (less likely to react with other chemicals) when they are closer to the nucleus.

n n Using this information, a system was devised to draw diagrams of atoms to show where electrons are located. A circle is drawn to represent the nucleus of an atom. Within this circle we write how many protons and neutrons are in the atom.

n n The next thing is to draw electron orbits around the nucleus. The number of orbits depends on how many electrons an atom has. Circles drawn on the orbits represent electrons.

Example n n Draw the Bohr-Rutherford diagram for lithium. Find out how many of each subatomic particle is in a lithium atom.

How many protons? 3 How many electrons? 3 How many neutrons? 4

Draw the nucleus n Then add the first electron orbit: n What is the maximum number of electrons allowed in the first orbit? 2 n Draw the electrons n Does lithium have more than 2 electrons? Yes. n Draw another electron orbit: n

n How many more electrons do we place in this orbit to show that lithium has three electrons altogether? 1 Draw the last electron

Lithium 3 p 4 n

Another Example n Draw the Bohr-Rutherford diagram for neon. How many protons? 10 How many electrons? 10 How many neutrons? 10

Neon n How many in the first orbit? 2 How many more do we need to get to 10? 8

Neon 10 p 10 n

n n Outside of the first orbit, electrons are usually drawn in pairs. Don’t’ forget the maximum number of electrons allowed in each orbit: • First orbit maximum 2 electrons • Second orbit maximum 8 electrons • Third orbit maximum 8 electrons

Bill Nye –The Atom n The Atom-Bill Nye the Science Guy

Homework n Bohr-Rutherford Diagrams • Compete the worksheet and hand in for marks n Due at the beginning of class tomorrow

Upcoming Events SUBATOMIC PARTICLE AND BOHR QUIZ • THURSDAY NOVEMBER 15 TH COMPUTER LAB FOR ELEMENT PROJECT • THURSDAY NOVEMBER 15 TH