Transcript Ions - Paint Valley High School

Ions
Atoms that are not
neutral
Atoms Are Neutral
• Let’s review: Why are atoms neutral?
–Because they have equal numbers of
protons and electrons.
Protons?
3
3 (same as atomic #)
Li
Neutrons?
7
Electrons?
4 (mass - atomic #)
3 (same as # of protons)
Why is this atom
neutral?
-
How many positive
charges?
-
o + o
o
+ +
o
3
-
How many negative
charges?
3
+3 + -3 = ?
0
Atoms can gain or lose
electrons.
• Atoms are the most stable when their outer
shells are full (like the Noble Gases).
What are two ways for
Lithium to have a
Noble Gas
o + o
configuration?
o
+ +
- 1. Lose 1 electron
o
2. Gain 7 electrons
-
Which is easier?
• Is it easier for Lithium to LOSE 1 electron, or
GAIN 7 electrons in order to have a full
outermost shell?
– Easier to LOSE 1
If Lithium LOSES 1
electron, is it neutral now?
NO! How many protons?
3
How many electrons?
2
+3 + -2 = +1 Charged Ion
-
o + o
o
+ +
o
-
Let’s try another element…
• How about Beryllium?
-
How can Beryllium achieve
a Noble Gas configuration?
-
LOSE 2 electrons
+ o +
o o o
+ o +
-
-
GAIN 6 electrons
Which is easier?
-
LOSE 2!
What is a Beryllium ion’s
charge?
-
-
+4 + -2 = +2 Charged ion
What about the other side of
the periodic table?
• Let’s try Fluorine!
o
+
+ o
o+
-
+
o
+o
o
+
LOSE 7 electrons
o
+ o
o+
+ o
o
-
-
GAIN 1 electron
Which is easier?
-
-
How can Fluorine achieve a
Noble Gas configuration?
GAIN 1!
What is a Fluorine ion’s
charge?
+9 + -10 = -1 Charged ion
A Neat Trick!
• To help you remember charges of ions of
some elements (this trick does NOT work
for transition metals).
+1
+2
+3 +4
-3
-2
-1
0
Learning Check!
•
1.
2.
3.
4.
5.
6.
See if you can use the new trick and the trick
you learned before to predict # of valence
electrons AND the ion charge for the following
Ion Charge
elements: Valence Electrons
+2
Calcium 2
1
+1
Sodium
-1
Chlorine 7
6
-2
Oxygen
4
+/- 4
Carbon
3
+3
Aluminum
Ions have different names
• Cation-an ion with a
positive charge.
• Easy way to remember:
cation has a “t,” which
looks like a + sign.
Ions have different names
•Anion-an ion with a
negative charge.
•Easy way to
remember: think “A N”
for “a negative” ion.