Isotopes and Ions

Isotopes

Atoms of the same element that have different masses

Have the same number of protons and electrons but different numbers of neutrons

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

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)

Example

Naturally occurring copper consists of 69.17% copper-63, which has an atomic mass of 62.929 599 and 30.83% copper-65, which has an atomic mass of 64.927 793. Find the average atomic mass of copper.

(.6917) X (62.929 599) + (.3083) X (64.927 793) =

43.5284 + 20.0172 = 63.55

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-

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