2. Ions Elemental Properties and Patterns

3. Valence Electrons are…? electrons responsible for the chemical properties of atoms, those in the outer energy level. Valence electrons - The s and p electrons in the outer energy level – the highest occupied energy level Core electrons – are those in the energy levels below.

4. The Octet Rule The “goal” of most atoms (except H, Li and Be) is to have an octet or group of 8 electrons in their valence energy level. By gaining or giving off electrons, atoms end up with the same number of electrons as the noble gas they are closest to This allows them to achieve the same energy state as a noble gas and become stable

5. Ions Metals generally give electrons, nonmetals take them from other atoms. Atoms that have gained or lost electrons are called ions. All ions end up having an electrical charge If an atom has lost an electron, is has a positive (+) charge while if an atom has taken an electron, it has a negative (-) charge

6. Ions Here is a simple way to remember which is the cation and which the anion: This is a cat-ion. This is Ann Ion. He’s a “plussy” cat! She’s unhappy and negative. +

7. Cation Formation 11p+ Na atom 1 valence electron Valence e- lost in ion formation. Energy shell disappears so atom looks like Ne

8. Anion Formation 17p+ Chlorine atom with 7 valence e- One e- is added to the outer shell.. Ion now looks like Ar

9. Ions So what determines if an atom will lose electrons or gain electrons and what their ending charge will be? The position of a group A element gives us a clue by telling us the number of outermost electrons (valence electrons) an atom has And the octet rule provides us with the rest of the information

10. Ions If you remember, the column number (in Roman numerals) for A group elements is the number of valence electrons an atom has (except for He) So lets look at column IA—all of these elements have only 1 valence electron in their outermost energy level This electron is lost very easily (remember trend for ionization energy)

11. Cations By losing 1 electron, the element now has 1 MORE proton than it has electrons giving it a +1 charge Column IIA elements all have 2 valence electrons in their outermost energy level so they lose 2 electrons obtaining a +2 charge This trend continues through column IVA where ions having a +4 charge form

12. Ions Okay, at this point I have to throw a curve at you It turns out that the first two elements of column IVA will also sometimes TAKE 4 electrons to reach a full octet This gives the ion more electrons than protons by 4 which gives the ion a charge of -4

13. Ions In column VA, some elements can only GIVE electrons while other elements can only TAKE electrons Elements in column VA have 5 valence electrons in their outermost energy level but some elements are metals and some are nonmetals (remember metals give up electrons easily while nonmetals take electrons easily)

14. Anions At this point, it is easier for nonmetallic atoms to GAIN electrons than to lose them (remember that both ionization energy and electron affinity increases as you go across a period) But how many electrons will these nonmetallic elements gain? Again, use the number of valence electrons the element has AND the octet rule

15. Anions Column VA through column VIIA NONMETALLIC elements will GAIN electrons until they have a total of 8 valence electrons To find out how many electrons these nonmetallic elements will gain (with the exception of He) just subtract the column number from 8---N has 5 valence electrons so it will take 3 electrons (8-5 = 3) giving it a charge of -3

16. Anions All of the atoms in column VIA have 6 valence electrons; metallic atoms will give up 6 electrons giving them a +6 charge while nonmetallic atoms will take 2 electrons (8- 6=2) giving them a -2 charge All the atoms in column VIIA have 7 valence electrons AND are all nonmetals so they will take 1 electron (8-7=1) giving them a -1 charge

17. Naming Ions For some ions, that name of the element changes For cations, just add the word “cation”. – Example, what would you name K + ? Potassium cation For anions, you change the ending to “ide”. – Example, what would you name Cl - ? Chloride, anion

18. Assignment p. 207: 30 - 32

19. Electron Dot diagrams are… A way of showing & keeping track of valence electrons. How to write them? Write the symbol - it represents the nucleus and inner (core) electrons Put one dot for each valence electron (8 maximum) They don’t pair up until they have to (Hund’s rule) X

20. The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons to show. l First we write the symbol. N l Then add 1 electron at a time to each side. l If there are more than 4 electrons, the rest will have to pair up. l We have now written the electron dot diagram for Nitrogen.

21. Formation of Cations Metals lose electrons to attain a noble gas configuration. They make positive ions (cations) If we look at the electron configuration, it makes sense to lose electrons: Na 1s 2 2s 2 2p 6 3s 1 1 valence electron Na 1+ 1s 2 2s 2 2p 6 This is a noble gas configuration with 8 electrons in the outer level.

22. Electron Dots For Cations Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electrons Ca

23. Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons Ca

24. Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons Forming positive ions Ca 2+ NO DOTS are now shown for the cation. This is named the “calcium ion”.

25. Electron Configurations: Anions Nonmetals gain electrons to attain noble gas configuration. They make negative ions (anions) S = 1s 2 2s 2 2p 6 3s 2 3p 4 = 6 valence electrons S 2- = 1s 2 2s 2 2p 6 3s 2 3p 6 = noble gas configuration. Halide ions are ions from chlorine or other halogens that gain electrons

26. Electron Dots For Anions Nonmetals will have many valence electrons (usually 5 or more) They will gain electrons to fill outer shell. P 3- (This is called the “phosphide ion”, and should show dots)

27. Stable Electron Configurations All atoms react to try and achieve a noble gas configuration. Noble gases have 2 s and 6 p electrons. 8 valence electrons = already stable! This is the octet rule (8 in the outer level is particularly stable). Ar

28. Assignment p. 207: 34 – 36 LDS worksheet