CATIONS AND ANIONS IONS

OBJECTIVES When you complete this presentation you will be able to … determine the number of valence electrons in an atom of a representative element. explain how the octet rule applies to atoms of metallic and nonmetallic elements. describe how cations form. describe how anions form.

VALENCE ELECTRONS Valence electrons The total number of s- and p-electrons For Groups 1 and 2, it is the same as the group number For Groups 13 – 18, it is the group number minus ten Electron dot structures Illustration of the number of electron dot structure It is a combination of both Paired electrons (lone pairs). Single electrons. Octet Rule Most atoms will want a total of 8 electrons as shared bonding electrons and lone pairs.

CATIONS Definition: Cations are ions with a positive charge. Due to a loss of one or more electrons In general, metals become cations. Formation For groups 1, 2, and 13, the loss of electrons will help to bring the atoms closer to an octet Closer to the electron configuration of a noble gas. Group 1 elements lose one electron. Group 2 elements lose two electrons. Group 13 elements lose three electrons.

CATIONS For example: Na (1s 2 2s 2 2p 6 3s 1 ) → Na + (1s 2 2s 2 2p 6 ) + e - Mg (1s 2 2s 2 2p 6 3s 2 ) → Mg 2+ (1s 2 2s 2 2p 6 ) + 2 e - Al (1s 2 2s 2 2p 6 3s 2 3p 1 ) → Al 3+ (1s 2 2s 2 2p 6 ) + 3 e -

ANIONS Definition: Anions are ions with a negative charge. Due to a gain of one or more electrons In general, nonmetals become anions. Formation For groups 15, 16, and 17, the gain of electrons will help to bring the atoms closer to an octet Closer to the electron configuration of a noble gas. Group 15 elements gain three electrons. Group 16 elements gain two electrons. Group 17 elements gain one electron.

ANIONS For example: P (1s 2 2s 2 2p 6 3s 2 3p 3 ) + 3 e - → P 3- (1s 2 2s 2 2p 6 3s 2 3p 6 ) S (1s 2 2s 2 2p 6 3s 2 3p 4 ) + 2 e - → S 2- (1s 2 2s 2 2p 6 3s 2 3p 6 ) Cl (1s 2 2s 2 2p 6 3s 2 3p 5 ) + e - → Cl - (1s 2 2s 2 2p 6 3s 2 3p 6 )

CHECK What is the ion produced by each of the following elements? FNS OKNa GaSrO CaIRa

CHECK What is the ion produced by each of the following elements? F - N 3- S 2- O 2- K + Na + Ga 3+ Sr 2+ O 2- Ca 2+ I - Ra 2+