1. Do Now (In your Tracker)  Read the article and underline any words that you do not know. Answer the following questions: 1. What is the main idea of the essay? 2. What conclusion did the author reach? How do you know? 3. How does this relate to science? Today’s Lesson Topic: Atomic Numbers and Isotopes!

2. Class Updates  Tutoring will be on Thursday this week NOT Tuesday.  The price of hot chips is now 10 energy bars  If you need to take the quiz make sure you do so—tutoring would be a great opportunity to do so!

3. Today’s Objective:  SWBAT characterize and classify elements based on their atomic structure.  Essential Question: how can elements with different number of neutrons be similar?

4. Atomic Number (Z): is the number of protons in the nucleus of the atom. Z=#p The number of protons (atomic number) determine the identity of an element.

5. What about the electrons? How many? Atoms have no overall electrical charge so, an atom must have as many electrons as there are protons in its nucleus. # p =# e The atomic number of an element also equals the number of electrons in a neutral atom of that element Z =#e

7. Ex: Sodium  What is the atomic number of Sodium?  How many protons does sodium have?  How many electrons does sodium have? 11

8. Mass Number (A): The sum of the protons and neutrons in the nucleus. A=#p + #n

9. Standard atomic Notation

10. Isotopes They have different mass numbers because they have different numbers of neutrons, but they have the same atomic number because they have the same number of protons. Atoms of the same element with Same number of protons Same number of electrons Different number of neutrons

11. Isotopes  Do isotopes have similar chemical properties? Why?  Yes – electrons are the same  Do they have similar physical properties? Why?  NO – mass is different.

13. Example: Isotopes of Carbon and Hydrogen protium deuteriumtritium HH H Isotopes of Carbon Isotopes of Hydrogen

14. Atomic Mass Unit is a unit used to compare the masses of atoms and has the symbol u or amu.

15. 1 amu or u is approximately equal to the mass of a single proton or neutron.

16. Carbon-12 Chemists have defined the carbon-12 atom as having a mass of 12 atomic mass units.

17. Atomic Mass is the weighted average mass of all the naturally occurring isotopes of that element.

19. Exit Ticket:  Answer the following on your own piece of paper.  1. What does an atomic number of an element determine?  2.What is an isotope?  3. Write the number of protons, neutrons and electrons for Carbon- 12.