Transcript Regents Chemistry - Forestville Central School / Overview

Regents Chemistry
 Agenda
– Review electronegativity worksheet
– Ions and polyatomic Ions
– Calculating charges worksheet
– HW: Finish worksheet
Charges on ions…review
 Cations – are positive ions that form as
a result of a loss of electrons
– Ex: Cu2+, K+
 Anions – are negative ions that form as
a result of a gain of electrons
– Ex: O2-, F-
Bonds
 Ionic substances result from the
donation of one or more electrons by a
metal and acceptance of the electrons
by a nonmetal
 Covalent bonds result from the sharing
of electrons
 We have seen two atoms bonded in
both of these ways…but can we have
more?
Polyatomic Ions
 Polyatomic ions are elements that are
covalently bonded together but contain an
overall net charge and the ability to act like
an ionic compound.
– Example
NO3-
SO42-
Calculating Overall Net Charge
We are given the overall net charge on
specific polyatomic ions on our
reference tables..however, we need to
understand how to calculate
these ourselves
NO3-
Can be viewed as
Assigned oxidation
Values from table
1 x 5+ = +5
5+
(NO3)-
2-
(N O3)3 x 2- = -6
5-6 = -1
Practice Problem
S O 426+
SO42-
2-
1 x +6 = +6
4 x –2 = -8
-8 +6 = -2
CN-
If both atoms have
multiple states, the
atom with the higher
electronegativity gets
the negative charge
1N x -3 = -3
1C x +2 = +2
-3 - +2 = -1
Why is this important?
 Polyatomic ions combine just like other
ions to form ionic substances
K+ + NO3-  KNO3
Cu2+ + NO3-  ? Cu(NO3)2
Worksheet
Practice
 Name the following:
 CaSO4
Calcium Sulfate
Sodium Oxalate
 Na2C2O4
Aluminum Nitrate
 Al(NO3)3
 Au2(SO3)3
Gold (III) Sulfite
Practice
 Write chemical formulas for the following:
Li2CO3
 Lithium Carbonate
KCN
 Potassium cyanide
Sn(MnO4)4
 Tin (IV) permanganate
 Copper (II) dichromate
CuCr2O7