1. Unit 3 Valence Electrons and Ions

2. Subatomic Particles In an atom Protons and neutrons are clumped together in a very small dense nucleus In an atom Protons and neutrons are clumped together in a very small dense nucleus The Electrons are found outside of the nucleus in various electron clouds The Electrons are found outside of the nucleus in various electron clouds

3. Principle Energy Levels The electron clouds are found at specific distances from the nucleus called Principle Energy Levels The electron clouds are found at specific distances from the nucleus called Principle Energy Levels Lowest energy levels are closest to the nucleus Lowest energy levels are closest to the nucleus Highest energy levels are farthest from the nucleus Highest energy levels are farthest from the nucleus The electrons in an atom will fill the lower energy levels before filling the higher energy levels The electrons in an atom will fill the lower energy levels before filling the higher energy levels

4. Energy Level ‘Clouds’ phycomp.technion.ac.il/~phr76ja/lecture1.html hoku.as.utexas.edu/.../a309f04/lect1cos.html

5. Bohr The Bohr model is used to show electron placements in the energy levels. The Bohr model is used to show electron placements in the energy levels. Elements in the same row of the periodic table have the same number of occupied energy levels Elements in the same row of the periodic table have the same number of occupied energy levels

6. Energy Levels First energy level- max 2 electrons Second energy level- max 8 electrons Third energy level- max 8 electrons Fourth energy level- max 18 electrons

7. Example 1: Boron Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Boron is located in Period 2 Period 1 contains 2 electrons Period 2 contains 3 electrons B

8. Example 2: Silicon Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Silicon is located in Period 3 Period 1 contains 2 electrons Period 2 contains 8 electrons Period 3 contains 4 electrons Si

9. Example 2: Calcium Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Calcium is located in Period 4 Period 1 contains 2 electrons Period 2 contains 8 electrons Period 3 contains 8 electrons Period 4 contains 2 electrons Ca

10. Valence Electrons The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons Valence electrons are important because they are the electrons involved in chemical reactions Valence electrons are important because they are the electrons involved in chemical reactions This means that the number of valence electrons determines an element’s chemical properties This means that the number of valence electrons determines an element’s chemical properties

11. Valence Electrons Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties. Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties. We skip over the transition metal section. We will learn why in January ~SKIP~

12. Example 1: Boron Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Boron is located in Period 2 Period 1 contains 2 electrons Period 2 contains 3 electrons B Boron has 3 valence electrons

13. Example 2: Silicon Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Silicon is located in Period 3 Period 1 contains 2 electrons Period 2 contains 8 electrons Period 3 contains 4 electrons Si Silicon has 4 valence electrons

14. Example 2: Calcium Electrons fill from lowest to highest (inside  outside) Electrons fill from lowest to highest (inside  outside) Calcium is located in Period 4 Period 1 contains 2 electrons Period 2 contains 8 electrons Period 3 contains 8 electrons Period 4 contains 2 electrons Ca Calcium has 2 valence electrons

15. Valence Electron Patterns 1 Valence 2 Valence 3 Valence 4 Valence 5 Valence 6 Valence 7 Valence 8 Valence ~SKIP~ Color this onto the first periodic table in your coloring book. Be sure to draw a key.

16. Ions When elements undergo chemical reactions they either share or exchange electrons with other elements. When elements undergo chemical reactions they either share or exchange electrons with other elements. Atoms that have either lost or gained electrons are called ions. Atoms that have either lost or gained electrons are called ions. Unlike neutral atoms, ions have a net charge. Unlike neutral atoms, ions have a net charge.

17. Ion Charges The number of electrons that it has lost or gained determines an ion’s charge The number of electrons that it has lost or gained determines an ion’s charge Ions that GAIN electrons have a NEGATIVE charge and are called anions. Ions that GAIN electrons have a NEGATIVE charge and are called anions. Ions that LOSE electrons have a POSITIVE Charge and are called cations. Ions that LOSE electrons have a POSITIVE Charge and are called cations.

18. Electrons are Lazy! In order to be a stable atom the outside shell must either be completely filled with electrons or emptied (leaving the next shell filled). In order to be a stable atom the outside shell must either be completely filled with electrons or emptied (leaving the next shell filled). To do this, you must decide if it’s easier to lose or gain electrons. To do this, you must decide if it’s easier to lose or gain electrons.

19. Lewis Dot Diagram When you draw these out use the symbol from the P.T. in place of the X. Example, for Sodium you would draw Na Na Dots go around the symbol 4 times and then begin to pair up

20. Move onto Page 3 Click to next slide to see an example Click to next slide to see an example

21. Column# # Valence # Gain to be 8 # Lose to be 0 Gain or Lose ? Charge? 11711+1 22 133 1+7 = 8 Valance Need to gain 1-1 = 0 Valance Need to lose Gain or Lose? Electrons are lazy and will do the easiest/lowest number Charge Losing E’s = + charge Gaining E’s = - charge

22. Move onto Page 4 READ THE DIRECTIONS IN THE MIDDLE! READ THE DIRECTIONS IN THE MIDDLE! Protons = Atomic number Protons = Atomic number Neutrons = Mass Number – Protons Neutrons = Mass Number – Protons All of these are neutral so Electrons=Protons All of these are neutral so Electrons=Protons –Valence Electrons are only the electrons on the last ring.

23. Move onto Page 5 Draw the Lewis Dot Diagram (LDD) for the neutral atom Draw the Lewis Dot Diagram (LDD) for the neutral atom For each problem For each problem –Draw the LDD –Indicate the number of valence electrons. –How many does it want to lose/gain? –If it lost/gained what would the charge be?