Atoms – The Electron Cloud

Parts of an Atom 2 main parts nucleus electron cloud. Electron Cloud Review…

Electron Cloud Most space between nucleus and electron cloud is empty. It is never known precisely where the electrons are inside the electron cloud. Electron Cloud Protons Neutrons Ask a student to identify what the line is pointing at, (nucleus) click and the answer will appear. Ask a student what two particles are found in the nucleus, (protons and neutrons) click and the answer will appear. Ask a student what the arrow is pointing at (electron cloud)

- Electron - Charge = - (negative) mass  0.0005 amu Sub-atomic particle Charge = - (negative) mass  0.0005 amu * 1836 electrons = mass 1 proton Location = electron cloud outside & around nucleus Size comparison – if you were able to blow up electrons, protons, and neutrons to be visible to the human eye, a grain of sand or salt or sugar would represent the electron, whereas a standard size marble would represent a proton or a neutron. Handing out these materials to the students will help them understand why the mass of an atom does not include electrons. [NOTE: The next slide is hidden, but has a chart showing all the information about each of the subatomic particles.] From Chem4Kids.com: CHARGE IT! Electrons are the negatively charged particles of atoms. Together, all of the electrons of an atom create a negative charge that balances the positive charge of the protons in the atomic nucleus. Electrons are extremely small compared to all of the other parts of the atom. The mass of an electron is almost 1,000 times smaller than the mass of a proton. Electrons are found in clouds that surround the nucleus of an atom. Because electrons move so quickly, it is impossible to see where they are at a specific moment in time. After years of experimentation, scientists discovered specific areas where electrons are likely to be found. These shells change depending on how many electrons an element has. The higher the atomic number, the more shells and electrons an atom will have.

How can you determine how many electrons are in an atom? In order for an element to be STABLE – the # of negative (-) subatomic particles MUST EQUAL the number of positive (+) subatomic particles. With a partner, discuss what that means. Through discussion, students should figure out that # of electrons equals the number of protons. IMPORTANT: The Atomic Number tells us the number of protons ONLY…we assume stability of the element and that the number of electrons is the same. DO NOT TELL students that the atomic number tells the number of protons AND electrons.

But where exactly are the electrons in an atom? Electron Clouds areas within atoms surrounding the nucleus where there is a high probability of finding electrons NOTE: Please help students understand that there are other names for orbitals including ‘energy levels’, ‘electron shells’, ‘shells’, as well as ‘orbitals’. These terms are often used interchangeably. From Chem4Kids.com: Electrons are found in clouds that surround the nucleus of an atom. Because electrons move so quickly, it is impossible to see where they are at a specific moment in time. After years of experimentation, scientists discovered specific areas where electrons are likely to be found. These shells change depending on how many electrons an element has. The higher the atomic number, the more shells and electrons an atom will have. Orbitals areas within the electron cloud with a higher probability of finding electrons

Orbital Levels closest to nucleus – max 2 electrons 2nd shell – max 8 electrons 3rd shell – max 8 electrons fill shells closest to nucleus first TEACHER NOTE: the term “shell” is used here to demonstrate there are various terms for the orbitals. We recommend that you use orbital, electron shell, electron cloud and circle, interchangeable throughout this unit so students are familiar with all the terms. Since electrons can be anywhere in the electron cloud, we use a model of circles (Bohr Model) to demonstrate the orbitals. This might be a good point to talk about the limitations of this model…electrons don’t travel in circular orbits; they are found somewhere in the cloud at any given moment…as an analogy, think about winding a ball of yarn: as you wind the yarn around the ‘ball’ and say “STOP”…you are somewhere in the “cloud” at that moment.

Build an atom… With your partner, use the Atom Model to create the following elements: Hydrogen Oxygen Fluorine Sodium Aluminum Argon Have students use the BRIGHT atom models to create each of the listed elements. There should also be a teacher model under the document camera… 1) After students complete their models, have one come up to the document camera and show their model; 2) Ask if the class agrees, if not have them discuss changes; 3) after all agree, the teacher states whether he/she agrees or disagrees; 4) If teacher disagrees, have students repeat steps 2 & 3. NOTE: Next slide is HIDDEN, but it has the Bohr models for each of the listed elements.

Follow the Electrons Use your Periodic Table to follow the elements and the “Bohr Model” for each. TEACHER NOTE: During the rest of the slides, it would be a great time to review Periodic table information such as the meaning of “Periods”. Valence electrons (Groups) will be introduced in the next PPT.

Hydrogen - NUCLEUS Have students locate the elements on the periodic table as you go through the next several slides. They should come to the conclusion that the period numbers indicate the number of electron shells and that the group numbers indicate the number of electrons in the last shell.

Helium - - NUCLEUS

Lithium - - - NUCLEUS

Beryllium - - - NUCLEUS -

Boron - - - NUCLEUS - -

Carbon - - - - NUCLEUS - -

Nitrogen - - - - - NUCLEUS - -

Oxygen - - - - - NUCLEUS - - -

Fluorine - - - - - - NUCLEUS - - -

Neon - - - - - - NUCLEUS - - - -

Sodium - - - - - - - NUCLEUS - - - -

Magnesium - - - - - - - NUCLEUS - - - - -

Aluminum - - - - - - - - NUCLEUS - - - - -

Silicon - - - - - - - - NUCLEUS - - - - - -

Phosphorus - - - - - - - - - NUCLEUS - - - - - -

Sulfer - - - - - - - - - NUCLEUS - - - - - - -

Chlorine - - - - - - - - - - NUCLEUS - - - - - - -

Argon - - - - - - - - - - NUCLEUS - - - - - - - -