1. Ions Chapter 7 Section 1

2. Valence Electrons Electrons in the highest occupied energy level of an element The number of valence electrons largely determines the chemical properties of an element The group number of the representative elements corresponds to the number of valence electrons

3. Lewis Structure The valence electrons are the only electrons used in chemical bonds. Therefore, only the valence electrons are shown in an electron dot structure also called a Lewis Structure Electron dot structures show the valence electrons as dots

4. Lewis Structures N O Na B

5. The noble gases are unreactive in chemical reactions because they all have 8 valence electrons except for He which has 2.

6. Octet Rule Gilbert Lewis explained why atoms form certain kinds of ions and molecules He called his explanation the octet rule: In forming compounds, atoms tend to achieve the electron configuration of a noble gas An octet is a set of 8 electrons (noble gases have 8 valence electrons)

7. Octet Rule Elements will behave differently based on the type of element Metals will lose their valence electrons so that their last energy level will have 8 valence electrons (Sodium wants an electron configuration like Ne) Nonmetals will gain electrons or share electrons with another nonmetal to gain electrons so the current energy level is an octet (Cl wants an electron configuration like Ar)

8. Ions Atoms are electrically neutral because it has equal numbers of protons and electrons An ion forms when an atom or groups of atoms loses or gains electrons 7.1

9. Formation of Cations An atom’s loss of valence electrons produces a cation or a positively charged ion Cations are produced by the loss of valence electrons from a metal The name of the cation has the same name as the element The sodium atom forms the sodium cation

10. Formation of Cations Sodium has 11 electrons, including 1 valence electron The sodium Ion has an electron configuration of Ne Sodium is now left with an octet 7.1

11. Formation of Cations The electron configuration of the sodium ion is the same as that of a neon atom. 7.1 Loss of a valence electron

12. Formation of Cations Using electron dot structures, you can show the ionization more simply. 7.1

13. Formation of Cations A magnesium atom attains the electron configuration of neon by losing both valence electrons. The loss of valence electrons produces a magnesium cation with a charge of 2+. 7.1

14. Formation of Cations Cations of Group 1A elements always have a charge of 1+. Cations of group 2A elements always have a charge of 2+. Cations of group 3A elements always have a charge of 3+ 7.1

15. Transition Metal Cations Transition metals will not lose electrons to match the noble gas before or after it. Silver would have to lose eleven to match krypton and gain seven to match xenon Instead it will lose its 5s 1 electron Pseudo noble gas configuration Ag 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 10 Ag + 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 4d 10

16. Formation of Anions The gain of negatively charged electrons by a neutral atom produces an anion. The name of an anion typically ends in -ide. – Chlorine becomes Chloride – Oxygen becomes Oxide Because they have almost full valence shells nonmetal elements gain noble gas configuration by gaining electrons 7.1

17. Formation of Anions A gain of one electron gives chlorine an octet and converts a chlorine atom into a chloride ion. It has the same electron configuration as the noble gas argon. 7.1

18. Formation of Anions Both a chloride ion and the argon atom have an octet of electrons in their highest occupied energy levels. 7.1 Gain of valence electrons

19. Formation of Anions In this equation, each dot in the electron dot structure represents an electron in the valence shell in the electron configuration diagram. 7.1

20. Formation of Ions Ions produced when chlorine and other halogens gain electrons are called halide ions All halide ions have a charge of 1-

21. Formation of Anions Oxygen is in Group 6A. 7.1 Gain of valence electrons

22. Formation of Anions Anions of Group 5A elements always have a charge of 3-. Anions of group 6A elements always have a charge of2-. Anions of group 7A elements always have a charge of 1-