1. Isotopes and Ions
Section 3-3 Continued

2. Isotopes Atoms of the same element that have different masses
Have the same number of protons and electrons but different numbers of neutrons

3. How many protons, neutrons, & electrons are in the following?
Bromine – 80
Write the hyphen notation for the element that contains 15 electrons and 15 neutrons
13C 6
35 p, 35 e, 45 n
Phosphorus – 30
6 p, 6 e, 7 n

4. Average Atomic Mass
Weighted average of the atomic masses of naturally occurring isotopes of an element
This is the number that appears on the periodic table
(abundance of isotope in decimal form) X (atomic mass of isotope) + (abundance of isotope in decimal form) X (atomic mass of isotope)

5. Example
Naturally occurring copper consists of 69.17% copper-63, which has an atomic mass of and 30.83% copper-65, which has an atomic mass of Find the average atomic mass of copper.
(.6917) X ( ) + (.3083) X ( ) =
= 63.55

6. Ions
An atom or group of bonded atoms that has a positive or negative charge
Positive ions have lost electrons. They have more protons than electrons. Ex: Ca2+
Negative ions have gained electrons. They have more electrons than protons. Ex: N3-

7. How many protons, neutrons, and electrons are in the following:
Na+
Cl-
Mg2+
O2-
Al3+
11 p, 12 n, 10 e
17 p, 18 n, 18 e
12 p, 12 n, 10 e
8 p, 8 n, 10 e
13 p, 14 n, 10 e