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4.10 Using Bohr’s Model of the Atom

4.10 Using Bohr’s Model of the Atom . (Sec 7.4 pg 218). Recall that Bohr’s model of the atom has electrons orbiting the nucleus, in defined electron shells . . The Bohr model can be represented very well with diagrams.

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4.10 Using Bohr’s Model of the Atom

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  1. 4.10 Using Bohr’s Model of the Atom (Sec 7.4 pg 218)

  2. Recall that Bohr’s model of the atom has electrons orbiting the nucleus, in defined electron shells.

  3. The Bohr model can be represented very well with diagrams. • This is done by drawing circles that represent the electron shells around the element symbol. • Then dots, representing the electrons, are added to the circles in sequential order from the inside to the outside. • Remember each shell con only hold a certain number of electrons! • 1st ring = 2 electrons • 2nd ring = 8 electrons • 3rd ring = 8 electrons

  4. Let’s take this fine opportunity to draw Bohr diagrams for the first 20 elements!

  5. We can also represent an ion (an atom that has a different amount of electrons than protons) with a Bohr diagram. • Normally P only has 15 electrons. This P ion has 3 additional electrons, giving it a charge of 3-.

  6. Bohr’s theory is supported by emission spectrum data. However, a really good theory also makes predictions about what kinds of observations you should see in future experiments (this is a good way to test a theory).

  7. One prediction from the Bohr model is that chemical reactivity is determined by the interaction of the outermost electrons in the atom. • This prediction suggests that an atom is most stable when it has a ‘full’ outer electron shell. (sometimes known as the ‘stable octet’ rule) • Further, this theory suggests that some elements like to ‘give up’ electrons, while others like to ‘gain’ electrons in order to have a ‘full’ outer electron shell.

  8. For example: • Lithium only needs to lose 1 electron to make the first electron shell its outermost ring. • Fluorine only needs to gain 1 electron to have a full outermost ring.

  9. This means that lithium should be able to lose its one ‘outer’ electron to fluorine.

  10. This will make lithium positively charged (less electrons than protons) and fluorine negatively charged (extra electrons). • Now they have opposite charges, and should be attracted to each other!

  11. It turns out that this does happen! The Bohr model can predict how atoms bond! This makes it a very strong theory. • Please note this type of attraction between atoms (‘bonding’) is called ionic bonding, and only occurs between metals and non-metals (more on this later)

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