1. Isotopes

2. Isotopes are atoms that have the same number of protons but different numbers of neutrons Most elements in the first two rows of the periodic table have at least 2 isotopes with one being more common than the other In nature, elements are almost always found as a mixture of isotopes

3. For example, the most common isotope of hydrogen has no neutrons at all There's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. Neutron Proton Isotopes of Hydrogen Most common isotope

4. To identify an isotope more specifically, chemists add a number after the elements name. ex. Carbon-11 Carbon-12 Carbon-14 This number is called the isotope’s mass number and is the sum of the isotope’s number of protons and neutrons. For example, an atom with 17 protons and 20 neutrons has a mass number of 37. More fun with Isotopes

5. Q. What is the mass of the Nitrogen isotope with 7 protons and 12 neutrons? A. Nitrogen-19

6. iodine-128 potassium-40 75 21 53 19 53 19 Atom Protons Electrons Neutrons Examples

7. Isotope Symbols 141 56 Mass number Atomic number Charge Ba 2+

8. How many protons, neutrons, and electrons are present? 56 26 STEP 1: The atomic number in the lower left corner = 26 protons. The difference between the mass number and the atomic number is 56 – 26 = 30 neutrons STEP 2: The charge on the ion, 2+ shows us that there are 2 more protons than electrons, indicating that there are 24 electrons. Fe 2+

9. Isotope Symbols 141 56 Mass number Atomic number Charge Ba 2+ Step 1) 141- 56= 85 neutrons Step 2) 56 electrons -2 = 54 electrons