Lesson 44 How are ions classified and name

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Lesson 44 How are ions classified and name ?

• How are ions classified ?
• How are ions named ?
• How are acids named ?
• Starting with an atom, how is a simple cation
  formed ?
• Starting with an atom, how is a simple anion
  formed ?
• How is a polyatomic ion formed ?
• What is the logic employed behind the naming of
  ionic compounds ?

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How are ions classified ?

• Depending on charge carrying, ions are classified
  as cations (positively charge) and anions
  (negatively charge).
• Depending on the number of atom present, ions can
  also be classified as simple ion (with 1 atom
  only) and polyatomic ion (with 2 or more atoms)

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Cation and Anion

• Positive ion Cation e.g. Na sodium ion

• Negative ion Anion e.g. Cl-chloride ion (not
  chlorine ion)

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How are ions named ?

• simple cation the same as the name of the atom
  e.g. sodium ion Na, copper(II) ion Cu2
• simple anion the same as the name of the atom
  but with an ending -ide. e.g. oxide ion O2-.

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Simple ion - oxide ion O2-
no. of proton in O 8 no. of electron 10 Total
charge (8) (-10) -2
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How are ions named ?

• simple cation the same as the name of the atom
  e.g. sodium ion Na, copper(II) ion Cu2
• simple anion the same as the name of the atom
  but with an ending -ide. e.g. oxide ion O2-.
• polyatomic cation ammonium ion NH4 is the only
  one being studied in Form 3.

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polyatomic ion - ammonium ion NH4
of p in N of p in 4 H 7 4 (1)
11 Total of e of p - 1 11 - 1 10
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How are ions named ?

• simple cation the same as the name of the atom
  e.g. sodium ion Na, copper(II) ion Cu2
• simple anion the same as the name of the atom
  but with an ending -ide. e.g. oxide ion O2-.
• polyatomic cation ammonium ion NH4 is the only
  one being studied in Form 3.
• polyatomic anion may end with -ide, -ite, -ate
  and begin with per-, thio, hypo-, hydrogen-, di-
  depending what atoms are present.

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Polyatomic cations Polyatomic anions   NH4 ammoni
um ion OH- hydroxide ion CN- cyanide
ion NO3- nitrate ion MnO4- permanganate
ion ClO3- chlorate ion SO42- sulpha
te ion CO32- carbonate ion Cr2O72- dichro
mate ion PO43- phosphate ion
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Naming of ions

• Meaning of some
• prefixes and suffixes Example
• di- two dichromate ion, Cr2O72-
• thio - replace O atom by S atom thiosulphate
  ion, S2O32-
• hydrogen- H ion hydrogencarbonate ion,
• HCO3-

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Naming of oxygen containing anion

• Oxygen containing compounds Example
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• per-ate O containing - even more O perchlorate
  ion,
• ClO4-
• -ate O containing - more O chlorate ion,
• ClO3-
• -ite O containing - less O chlorite ion,
• ClO2-
• hypo-ite O containing - even less O hypochlorite
  ion,
• ClO-

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Announcement

• There will be a quiz on the name of the 10
  polyatomic ions mentioned.

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Important polyatomic ions
NH4
OH-
CN-
NO3-
MnO4-
ClO3-
SO42-
CO32-
Cr2O72-
PO43-
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Covalent bond within a polyatomic ion

• Polyatomic ion e.g. hydroxide ion, OH-
• no. of proton in O no. of proton in H
• 8 1 9
• no. of electron 10
• Total charge (9) (-10) -1

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How are acids named ?
Acid - an electrolyte which ionizes in water to
give H(aq) as the only cation. Acid ?
H(aq) Anion(aq)

• Name of parent acid Corresponding anion
• hydrochloric acid (HCl(aq)) chloride ion (Cl-)
• sulphuric acid (H2SO4(aq)) sulphate ion (SO42-)
• nitric acid (HNO3(aq)) nitrate ion (NO3-)
• carbonic acid (H2CO3(aq)) carbonate ion (CO32-)

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Names of oxygen containing acids

• Sulphate ion SO42-Sulphuric acid H2SO4
• Sulphite ion SO32-Sulphurous acid H2SO3
• Nitrate ion NO3-Nitric acid HNO3
• Nitrite ion NO2-Nitrous acid HNO2

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Starting with an atom, how is a simple cation
formed ?

• Starting with an atom (though this is not the
  only way), a simple cation is formed by losing
  the outermost shell electron until the atom
  attains a complete filled outermost shell (a
  typical behavior of metal atom having low
  electronegativity).

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Starting with an atom, how is a simple anion
formed ?

• Starting with an atom (though this is not the
  only way), a simple anion is formed by gaining of
  electron until the atom attains a completely
  filled outermost shell (a typical behavior of
  non-metal atom having high electronegativity).

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How is a polyatomic ion formed ?

• The presence of polyatomic ion cannot be
  explained satisfactorily if we assume that all
  ions are coming from atom.
• Formation of polyatomic ion can be considered as
  different numbers of proton and electron sticking
  together to form a charged particle with multiple
  nuclei.

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What is the logic employed behind the naming of
ionic compounds ?

• The name of an ionic compound is comprised of the
  name of the constituent ions present.
• By the fact that all stable compounds are
  electrically neutral, the name of an ionic
  compound is not related to the actual ratio of
  the cation and anion present.

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Classwork(Do them on your textbook)

• pg164 Q8.7,Q8.8
• pg179 Q6,7,8,12,13,14,15,16