1. Exploring Inner Space TEKS 8.5A describe the structure of atoms including the masses, electrical charges and locations, of protons and neutrons in the nucleus and electrons in the electron cloud TEKS 8.5B identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity

2. All matter is made up of atoms.

3. Protons Neutrons Electrons All atoms are made up of

4. Each particle has specific properties, such as location, electric charge and mass.

5. All atoms of the same element have same number of. All atoms of the same element have same number of protons. *Ex. All Hydrogen atoms have 1 proton.

6. The number of protons determines the The number of protons determines the element’s identity. atomic number = # of Protons.

7. Structure of the Atom

8. The Nucleus The center of the atom is called the nucleus. proton neutron nucleus 3 Li 6.941 Lithium

9. The nucleus contains protons and neutrons.

10. The nucleus makes up the mass of an atom.

11. Atomic Mass = # Protons + # Neutrons Proton = 1 atomic mass unit (amu) Neutron = 1 atomic mass unit (amu)

12. If Lithium has 3 protons and 4 nuetrons, what is the atomic mass of the atom? 7

13. The Periodic Table shows the atomic mass for each element as a. The Periodic Table shows the atomic mass for each element as a decimal. mic mass to find the number of protons or neutrons. Round the atomic mass to find the number of protons or neutrons.

14. If the mass number is known, and you know the number of protons, how can you find the number of neutrons? # Neutrons = Mass # - # Neutrons = Mass # - # Protons

15. The Electron Cloud and Energy Levels Surrounding the nucleus is the electron cloud. Electrons orbit around the nucleus in different energy shells (levels).

16. energy levels

17. Electrons are so small that they are NOT included in the atomic mass.

18. Energy levels can only hold a certain number of electrons in each energy level. The energy level holds up to electrons. The first energy level holds up to 2 electrons. The energy level holds up to electrons. The second energy level holds up to 8 electrons. The energy level may hold or more electrons. The third energy level may hold 8 or more electrons.

19. first energy level

20. second energy level

21. third energy level 8 or more!

22. How many electrons are in each energy level of the element Lithium? 1 st – 2, 2 nd – 1 electron energy levels 3 Li 6.941 Lithium electron cloud

23. Valence Electrons Valence electrons are the # of electrons in the outer most energy level.

24. Valence electrons….. valence electrons are found here!

25. Valence electrons determine how it is with other elements. Valence electrons determine how reactive it is with other elements.

26. Charges on particles Protons = charge. Protons = positive charge. Electrons = charge. Electrons = negative charge. Neutrons = have charge. Neutrons = have no charge.

27. A stable atom has the same number of protons and electrons. 8 Protons + + + + + + + + 8 Electron - - - - - - - - = NO CHARGE = STABLE ATOM

28. The positive and negative charges cancel out and there is no charge.

29. Particle Charge Mass Location Proton Neutron Electron EXIT TICKET