Post on 13-Jan-2016
C AT I O N S A N D A N I O N S
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 (1s2 2s2 2p6 3s1) → Na+ (1s2 2s2 2p6) + e-
Mg (1s2 2s2 2p6 3s2) → Mg2+ (1s2 2s2 2p6) + 2 e-
Al (1s2 2s2 2p6 3s2 3p1) → Al3+ (1s2 2s2 2p6) + 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 (1s2 2s2 2p6 3s2 3p3) + 3 e- → P3- (1s2 2s2 2p6 3s2 3p6)
S (1s2 2s2 2p6 3s2 3p4) + 2 e- → S2- (1s2 2s2 2p6 3s2 3p6)
Cl (1s2 2s2 2p6 3s2 3p5) + e- → Cl- (1s2 2s2 2p6 3s2 3p6)
CHECK
• What is the ion produced by each of the following elements?
F N S
O K Na
Ga Sr O
Ca I Ra
CHECK
• What is the ion produced by each of the following elements?
F- N3- S2-
O2- K+ Na+
Ga3+ Sr2+ O2-
Ca2+ I- Ra2+