6 Questions
What is the net electric charge of a polyatomic ion?
A group of atoms bonded together with a net electric charge
What is the valence number of an atom in its elemental form?
0
Which of the following polyatomic ions has a charge of -2?
Carbonate (CO32-)
What is the valence number of nitrogen in ammonia (NH3)?
-3
What is the sum of the valence numbers of the individual atoms in a neutral compound?
0
What is the valence number of carbon in methane (CH4)?
+4
Study Notes
Polyatomic Ions
- A polyatomic ion is a group of atoms bonded together that has a net electric charge.
- They are also known as complex ions.
- Polyatomic ions are typically formed from a combination of nonmetal atoms.
Common Polyatomic Ions
- Ammonium (NH4+)
- Carbonate (CO32-)
- Hydroxide (OH-)
- Nitrate (NO3-)
- Phosphate (PO43-)
- Sulfate (SO42-)
Valence Numbers (Oxidation States)
- A valence number, also known as an oxidation state, is a number that represents the number of electrons an atom gains or loses to form a bond.
- Valence numbers can be positive or negative.
- The sum of the valence numbers in a neutral compound is zero.
Rules for Assigning Valence Numbers
- Atoms in their elemental form: Valence number of zero.
- Monatomic ions: Equal to the charge of the ion (e.g., Na+ = +1, Cl- = -1).
- Polyatomic ions: The sum of the valence numbers of the individual atoms in the ion.
- Compounds: The sum of the valence numbers of the individual atoms in the compound is zero.
Examples of Valence Numbers
- Sodium (Na): +1
- Chlorine (Cl): -1
- Oxygen (O): -2
- Nitrogen (N): -3 in ammonia (NH3), +5 in nitrate (NO3-)
- Carbon (C): +4 in methane (CH4), -4 in methide (CH3-)
Polyatomic Ions
- A polyatomic ion is a group of atoms bonded together with a net electric charge, also known as a complex ion.
- Polyatomic ions are typically formed from a combination of nonmetal atoms.
Examples of Polyatomic Ions
- Ammonium (NH4+)
- Carbonate (CO32-)
- Hydroxide (OH-)
- Nitrate (NO3-)
- Phosphate (PO43-)
- Sulfate (SO42-)
Valence Numbers (Oxidation States)
- A valence number, also known as an oxidation state, represents the number of electrons an atom gains or loses to form a bond.
- Valence numbers can be positive or negative.
- In a neutral compound, the sum of the valence numbers is zero.
Rules for Assigning Valence Numbers
- Atoms in their elemental form have a valence number of zero.
- Monatomic ions have a valence number equal to the charge of the ion.
- Polyatomic ions have a valence number equal to the sum of the valence numbers of the individual atoms in the ion.
- In a compound, the sum of the valence numbers of the individual atoms is zero.
Examples of Valence Numbers
- Sodium (Na): +1
- Chlorine (Cl): -1
- Oxygen (O): -2
- Nitrogen (N): -3 in ammonia (NH3), +5 in nitrate (NO3-)
- Carbon (C): +4 in methane (CH4), -4 in methide (CH3-)
Learn about polyatomic ions, also known as complex ions, and valence numbers or oxidation states in chemistry. Understand how polyatomic ions are formed and review common examples.
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