1.3 Ions and Ion Formation PDF

1.3 Ions and Octet Rule 1  Octet Rule An octet means 8 valence electrons. is associated with the stability of the noble gases. Exception: Helium (He) is stable with 2 valence electrons. Electron level arrangement valence electrons He 2...

1.3 Ions and Octet Rule 1  Octet Rule An octet means 8 valence electrons. is associated with the stability of the noble gases. Exception: Helium (He) is stable with 2 valence electrons. Electron level arrangement valence electrons He 2 2 Ne 2, 8 8 Ar 2, 8, 8 8 Kr 2, 8, 18, 8 8 2  Ionic and Covalent Bonds Atoms form octets to become more stable. by losing, gaining, or sharing valence electrons. by forming ionic bonds or covalent bonds. 3  Metals Form Positive Ions Metals form positive ions “cations” by a loss of their valence electrons. with the electron configuration of the nearest noble gas. that have fewer electrons than protons. Group 1 metals ⎯→ ion 1+ Group 2 metals ⎯→ ion 2+ Group 3 metals ⎯→ ion 3+ 4  + Formation of a Sodium Ion, Na Sodium achieves an octet by losing its one valence electron. 5  + Charge of Sodium Ion, Na With the loss of its valence electron, the sodium ion has a +1 charge. Sodium atom Sodium ion 11p+ 11p+ 11e- 10e- 0 1+ 2, 8 6  2+ Formation of Mg Magnesium achieves an octet by losing its two valence electrons. 2, 8, 2 2, 8 7  Learning Check A. The number of valence electrons in aluminum is 1) 1e-. 2) 2e-. 3) 3e-. B. The change in electrons for octet requires a 1) loss of 3e-. 2) gain of 3e-. 3) a gain of 5e-. C. The ionic charge of aluminum is 1) 3-. 2) 5-. 3) 3+. D. The symbol for the aluminum ion is 1) Al3+. 2) Al3-. 3) Al+. 8  Formation of Negative Ions In ionic compounds, nonmetals achieve an octet arrangement. gain electrons. form negatively charged ions with 3-, 2-, or 1- charges. Negative ions are referred to as “anions” 9  - Formation of a Chloride, Cl Chlorine achieves an octet by adding an electron to its valence electrons. 2, 8, 7 2, 8, 8 10  - Charge of a Chloride Ion, Cl By gaining one electron, the chloride ion has a -1 charge. Chlorine atom Chloride ion 17p+ 17p+ - + 1 e- 17e 18e- 0 1– 11 Some Ionic Charges I- 12 Polyatomic Ions 13  Polyatomic Ions A polyatomic ion is a group of atoms. has an overall ionic charge. Some examples of polyatomic ions are NH4+ ammonium OH− hydroxide NO3− nitrate NO2− nitrite CO32− carbonate PO43− phosphate HCO3− hydrogen carbonate (bicarbonate) 14 Names and Formulas of Common Polyatomic Ions 15 Names and Formulas of Common Polyatomic Ions 16