Polyatomic Ions

Question 1

Charge of nitrate - NO3 ion

Answer 1

1- - minus 1

Way to remember : HNO3 - nitric acid

Question 2

Charge of nitrite - NO2 ion

Answer 2

-1 - negative 1 charge

Question 3

Charge of phosphate ion PO4

Answer 3

3- (PO4 3-)

Way to remember (phosphoric acid) : H3PO4

Question 4

Charge of carbonate ion CO3

Answer 4

2- (CO3 2-)

Question 5

Charge of Sulfate ion

Answer 5

2- (SO42-)

—> way to remember : H2SO4

Question 6

Explain the bonding in the Nitrate (NO3^-1 ion)

Answer 6

-Nitrogen forms four bonds with 3 oxygen atoms
-3 of the bonds are normal covalent bonds
-the last bond is a dative covalent bond from nitrogen to oxygen, as nitrogen has already used 3 of its valence electrons in covalent bond but has a lone pair left

-2 of the oxygens have to gain an external electron as they only have 1 bond to nitrogen (1 has 1 covalent and 1 has 1 dative covalent bond)
-However the dative covalent bond gives nitrogen a partial positive charge
-so the overall change of the polyamtoic ion is -2 + 1 = -1

Question 7

Why can’t nitrogen expand its octet?

Answer 7

-It’s electron configurations is 1s2 2s2 2p3 , it does not have a d subshell and therefore no vacant d orbitals to promote electrons to

• Promoting an electron from the 2p to the 3s sub shell would take way too much energy anyway (you’re going up a whole shell) , and is not worth the pay off, as the atom can be stable without expanding its octet