2. IONS IONS are atoms or groups of atoms with a positive or negative charge.

3. When an atom or molecule gains or loses an electron it becomes an ion. A cation has lost an electron(s) and therefore has a positive charge ex. Mg 2+ Mg + 2e -  Mg 2+

4. An anion has gained an electron(s) and therefore has a negative charge ex. N 3- N + 3e -  N 3-

5. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript!

6. Na + I - Ca +2 O -2 Na I Ca O Which are the ions? anions? cations? elements?

7. Why would an element lose or gain an electron?

8. To become a couch potato!

9. Which means in chemistry lingo??????

10. GET STABLE! BE AN OCTET!

11. Get the electron configuration of the nearest noble gas Either a stable ____________ (or a stable __________ if you are lithium or beryllium)

12. PREDICTING ION CHARGES Mg What is the closest noble gas?

13. Does Mg need to lose or gain electron(s) to have the couch potato configuration of neon?

14. Prediction: Mg 2+

15. PREDICTING ION CHARGES F What is the closest noble gas?

16. Does F need to lose or gain electron(s) to have the couch potato configuration of neon?

17. Prediction: F -

18. Charges on Common Ions -2-3 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 18 atom.

19. Charges on Common Ions -2-3 +1 +2 Another way to think about this: look at the group number!

20. In general metals (Mg) lose electrons ---> cations (Mg 2+ ) ons (F - ) nonmetals (F) gain electrons -- -> anions (F - )

21. How would you write the symbol for the sodium ION?

22. How many valence electrons does sodium have?

23. It has 1…remember the group number!

24. Na +1

25. Learning Check – Counting State the number of protons, neutrons, and electrons in each of these ions. 39 K + 16 O -241 Ca +2 19 8 20 #p + ___________________ #n o ___________________ #e - ___________________

26. Remember an electron is negatively charged. When you lose them an atom becomes a positively charged ion…

27. When an atom gains electrons it becomes a ___________ charged ion