1. Here we’ll have a look at what atoms and ions are, and how atoms change into ions. We’ll start off by looking at how metal atoms form ions.

2. n n n In the center of all atoms there is a nucleus n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

3. n n n A nucleus is made up of protons and neutrons. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons protons and neutrons

4. n n n The nucleus we’ve shown here is the nucleus of a magnesium atom. The box for magnesium on the periodic table is shown on the left. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

5. n n n The atomic number is located on top of the element’s symbol on the periodic table. For magnesium, the atomic number is 12 n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

6. n n n The atomic number tells us the number of protons in the nucleus of an element’s atom. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

7. n n n So a nucleus of magnesium has 12 protons. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

8. n n n 12 protons are drawn in this model here n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

9. n n n The nuclei of most magnesium atoms have 12 neutrons. Just be aware that number of neutrons in a nucleus is not always equal to the number of protons. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons

10. n n n Neutrons have no charge, so the number of neutrons an atom contains, has no effect on the charge of ions that form. Only protons and electrons determine ion charges. n p n n p p p n p n p n p p n p n p n p p The nucleus of a magnesium atom 12 protons 12 neutrons Neutrons have no charge so they have no effect on the charge of an ion

11. n n n All protons have a positive charge n p n n p p p n p n p n p p n p n p n p p Protons have a positive (+) charge

12. n n n So we’ll change the p’s in our diagram to positive charges. n + n n + + + n + n + n + + n + n + n + + Protons have a positive (+) charge

13. n n n Because neutrons have no charge, we’ll just leave these with the letter “n”. n + n n + + + n + n + n + + n + n + n + + Neutrons have no charge, or a charge of 0

14. n n n There are 12 positively charged protons in the a magnesium nucleus, so the nucleus of a magnesium atom n + n n + + + n + n + n + + n + n + n + + The nucleus of a magnesium atom has a total charge of +12

15. n n n has a total charge of positive 12. (hold before clicking) n + n n + + + n + n + n + + n + n + n + + The nucleus of a magnesium atom has a total charge of +12 +12

16. n n n Electrons have a negative charge. So a neutral atom of magnesium must have 12 electrons to balance the positive 12 charge on the nucleus n + n n + + + n + n + n + + n + n + n + + A neutral atom of magnesium has 12 electrons +12 The nucleus of a magnesium atom has a total charge of +12

17. Here, we’ll use the Bohr Model of the atom, where the electrons occupy shells around the nucleus. electrons in shells 2, 8, 2 A neutral atom of magnesium has 12 electrons

18. The first shell has two electrons, the maximum number it can hold. – – electrons in shells 2, 8, 2 A neutral atom of magnesium has 12 electrons

19. The second shell has 8 electrons, the maximum number it can hold. That’s 2 plus 8, which is a total of 10 so far. And magnesium has 12 electrons.. – – ––––– – – – electrons in shells 2, 8, 2 A neutral atom of magnesium has 12 electrons

20. So the 3 rd shell of a magnesium atom has 2 electrons – – – ––––– – – – – electrons in shells 2, 8, 2 A neutral atom of magnesium has 12 electrons

21. So this accounts for 2 + 8 + 2 which equals all 12 electrons in a magnesium atom. – – – ––––– – – – – electrons in shells 2, 8, 2 A neutral atom of magnesium has 12 electrons

22. The nucleus has 12 protons and 12 neutrons. Instead of a picture, this is usually simplified by showing a circle (click) with 12 p and 12 n – – – ––––– – – – – 12 p 12 n

23. So this is how we represent a neutral magnesium atom. – – – ––––– – – – – 12 p 12 n a magnesium atom

24. The third shell of a magnesium atom is not filled. Atoms with partially filled shells tend to be unstable, so this atom is unstable. – – – ––––– – – – – 12 p 12 n a magnesium atom The third shell is not filled, so this atom is unstable

25. In order to become stable, this atom will (click) lose these two electrons in the third shell – – – ––––– – – – – 12 p 12 n a magnesium atom In order to become stable, this atom will lose these two electrons

26. Like this – – – ––––– – – – – 12 p 12 n a magnesium atom

27. This is no longer called a magnesium atom, we must now (click) call it a magnesium ion. – – ––––– – – – 12 p 12 n a magnesium atom a magnesium ion

28. In an ion, the number of electrons is NOT equal to the number of protons. We have 12 protons, but only 10 electrons here, so this is an ion – – ––––– – – – 12 p 12 n In an ion, the number of electrons is NOT equal to the number of protons a magnesium ion

29. This ion is stable. – – ––––– – – – 12 p 12 n This ion is stable. It has the same electron arrangement as the noble gas neon: completely filled first and second shells a magnesium ion

30. (start new sentence) Because it has 10 electrons, it has the same electron arrangement as the noble gas neon: – – ––––– – – – 12 p 12 n This ion is stable. It has the same electron arrangement as the noble gas neon: completely filled first and second shells a magnesium ion

31. With completely filled first, – – ––––– – – – 12 p 12 n This ion is stable. It has the same electron arrangement as the noble gas neon: completely filled first and second shells a magnesium ion

32. And second shells – – ––––– – – – 12 p 12 n This ion is stable. It has the same electron arrangement as the noble gas neon: completely filled first and second shells a magnesium ion

33. This ion has 12 protons, – – ––––– – – – 12 p 12 n 12 protons (+) a magnesium ion

34. But only 2 plus 8, or 10 electrons – – ––––– – – – 12 p 12 n 12 protons (+) 10 electrons (–) a magnesium ion

35. 12 protons means the ion has 12 positive charges – – ––––– – – – 12 p 12 n a magnesium ion 12 protons (+) 10 electrons (–) ++++++++++++

36. And 10 electrons means it has 10 negative charges – – ––––– – – – 12 p 12 n 12 protons (+) 10 electrons (–) ++++++++++++ –––––––––– a magnesium ion

37. Negative and positive charges neutralize each other, and what’s left over is called.. – – ––––– – – – 12 p 12 n 12 protons (+) 10 electrons (–) ++++++++++++ –––––––––– a magnesium ion

38. The net charge – – ––––– – – – 12 p 12 n 12 protons (+) 10 electrons (–) ++++++++++++ –––––––––– Net charge: ++ Net charge: +2 a magnesium ion

39. Which are two positive charges in this case. – – ––––– – – – 12 p 12 n ++++++++++++ –––––––––– Net charge: ++ Net charge: +2 a magnesium ion 12 protons (+) 10 electrons (–)

40. We can also state this by saying that the charge on this ion is positive 2. – – ––––– – – – 12 p 12 n ++++++++++++ –––––––––– Net charge: ++ Net charge: +2 a magnesium ion 12 protons (+) 10 electrons (–)

41. Which can also be written as 2 plus – – ––––– – – – 12 p 12 n ++++++++++++ –––––––––– Net charge: ++ Net charge: 2+ a magnesium ion 12 protons (+) 10 electrons (–)

42. In the box on the periodic table, the top right hand corner shows the charge on the most common ion of magnesium. We see it is (click) 2 plus – – ––––– – – – 12 p 12 n ++++++++++++ –––––––––– Net charge: ++ Net charge: 2+ The ion charge a magnesium ion 12 protons (+) 10 electrons (–)

43. The same as the net charge on our magnesium ion here. – – ––––– – – – 12 p 12 n 12 protons (+) 10 electrons (–) ++++++++++++ –––––––––– Net charge: ++ Net charge: 2+ The ion charge a magnesium ion

44. Looking on the periodic table, Group 1 metals, or alkali metals all lose 1 electron (click) to form an ion with a positive 1 charge. Group 1 (Alkali Metals) all lose one electron to form an ion with a 1+ charge

45. Group 2 metals, or alkaline earth metals all lose 2 electrons (click) to form an ion with a positive 2 charge. In general, metals tend to lose electrons in order to form stable positive ions. Group 2 (Alkaline Earth Metals) all lose two electrons to form an ion with a 2+ charge