addnotes15 - CHAPTER NOTES CHAPTER 15 Ionic Bonding and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER NOTES – CHAPTER 15 Ionic Bonding and Ionic Compounds Goals : To gain an understanding of : 1. Valence electron and electron dot notation. 2. Stable electron configurations. 3. Ionic and metallic bonding. NOTES: Valence electrons are the electrons in the highest energy level of an atom. For example, in the calcium atom (electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 ) the 4s 2 electrons are the valence electrons. In the titanium atom (electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 ) The 4s 2 electrons are still the valence electrons -they are in the highest energy level. In the phosphorus atom (electron configuration 1s 2 2s 2 2p 6 3s 2 3p 3 ) the 3s 2 3p 3 are the valence electrons. The valence electron numbers of the representative elements are: Group 1 - 1 valence electron Group 2 - 2 valence electrons Group 13 - 3 valence electrons Group 14 - 4 valence electrons Group 15 - 5 valence electrons Group 16 - 6 valence electrons Group 17 - 7 valence electrons Group 18 - 8 valence electrons Dot formulas use dots surrounding the symbol of the element to represent the valence electrons. The dot formulas for period 2 and 3 would appear as follows. Note electrons are usually shown as far apart as possible -they have the same charge and therefore repel each other. The Noble gases (Group 0) have a stable electron configuration (s 2 p 6 ) with 8 electrons filling the outer s and p orbitals. This stability comes from the low energy state of this configuration and also accounts for the low reactivity of these elements (most elements react with other elements to get to a lower, more stable energy state). For example the halogens (Group 7A) have 7 valence electrons (s 2 p 5 ) and want to gain one electron to get the low energy, stable electron configuration of the noble gases. The elements in group 6 (s 2 p 4 ) want to gain 2 electrons to get the low energy, stable electron configuration of the noble gases. The Group 1A elements (s 1 ) want to lose their outer electron to empty their outer shell and get a stable electron configuration. For example if sodium (1s 2 2s 2 2p 6 3s 1 ) loses its 3s 1 electron it will have filled s and p orbitals in its outer energy level. Gilbert Lewis, in 1916, proposed the octet rule : Atoms react by changing their number of electrons so as to acquire the stable electron configuration of a noble gas (s 2 p 6 ). An exception to the octet rule is the electron configuration of helium. Helium(1s
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 5

addnotes15 - CHAPTER NOTES CHAPTER 15 Ionic Bonding and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online