1. Unit 4 - Ions

2. Ions IONS - atoms that have gained or lost electrons
Charged particles because unequal number of p+ and e-
Metals lose electrons to form CATIONS (positively charged ions)
Non-metals gain electrons to form ANIONS (negatively charged ions)
A Negative ION

3. Ions
Metals LOSE electrons.
Non-metals GAIN electrons.

4. Ion Notation HOW TO WRITE AN ION: ELEMENT SYMBOLCharge
** Charge is a SUPERSCRIPT
Examples: Na charge = +1
O charge = -2
Al charge = +3

5. Practice
Find the number of protons, neutrons & electrons:
p+ n0 e-
23Na+
16O2–
12C

6. Practice
Find the number of protons, neutrons & electrons:
p+ n0 e-
23Na
16O2–
12C

7. The Octet Rule
The maximum number of valence electrons is 8 electrons: OCTET RULE.
Atoms form bonds to have a full shell of valence electrons: the same number of electrons as the closest noble gas.
In ionic bonds, atoms LOSE or GAIN electrons to meet the octet rule.

8. Electronegativity How “greedy” an atom is for electrons.
Strong electronegativity = greedy, steals electrons
Weak electronegativity = not greedy, gives away electrons
Give away electrons
Steal electrons

9. Formation of Cations
Metals have LOW electronegativity and LOW ionization energy so they will LOSE electrons to form cations.

10. Ionization
The process of when a metal loses electrons to become an ion. -
+4 protons
- 4 electrons
0 charge -
+4 protons
3 electrons
+1 charge + + + +
+4 protons
2 electrons
+2 charge - -

11. Formation of Anions
Non-metals have HIGH electronegativity and HIGH ionization energy so they will GAIN electrons to form anions, negative ions.

12. Ionization
The process of when a non-metal gains electrons to become an ion. -
+8 protons
- 8 electrons
0 charge - - - +
+8 protons
9 electrons
-1 charge + + - - + + + + +
+8 protons
10 electrons
-2 charge - - - -

13. Ions
Atoms of metals (3 or less valence electrons) lose their valence electrons.
Atoms of non-metals (5 or more valence electrons) gain electrons.

14. Charges of Ions Chlorine ion: Chlorine atom: 18 electrons 18-
17 protons 17 +
Neutral 0
Chlorine ion:
18 electrons 18-
17 protons 17 +
Net charge 1-
Magnesium atom:
12 electrons 12-
12 protons 12 +
Neutral 0
Magnesium ion:
10 electrons 10-
12 protons 12 +
Net charge 2+

15. Predicting Ionic Charges
Group 1A:
Lose 1 electron to form 1+ ions H+
Li+
Na+ K+
Rb+

16. Predicting Ionic Charges
Group 2A:
Loses 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+

17. Predicting Ionic Charges
Loses 3
electrons to form
3+ ions
Group 3A:
B3+
Al3+
Ga3+

18. Predicting Ionic Charges
Neither! Group 4A elements rarely form ions
EXCEPTION: Sn and Pb!! Treat like transition metals
Do they lose 4 electrons or gain 4 electrons?
Group 4A:

19. Predicting Ionic Charges
Nitride
Gains 3
electrons to form
3- ions
Group 5A:
P3-
Phosphide
As3-
Arsenide

20. Predicting Ionic Charges
Oxide
Gains 2
electrons to form
2- ions
Group 6A:
S2-
Sulfide
Se2-
Selenide

21. Predicting Ionic Charges
Gains 1 electron to form
1- ions
Group 7A:
F1-
Fluoride
Br1-
Bromide
Cl1-
Chloride
I1-
Iodide

22. Predicting Ionic Charges
Stable noble gases do not form ions!
Group 8A:

23. Predicting Ionic Charges
Some transition elements have only one possible charge:
Silver = Ag+
Zinc = Zn2+
Cadmium = Cd2+

24. Predicting Ionic Charges
Many transition metals and Pb and Sn (Group 4A)
have more than one possible charge.
Iron (III) = Fe3+
Iron (II) = Fe2+

25. Predicting Ionic Charges
For transition metals and Pb and Sn: use a Roman numeral to show the charge
Iron (II) = Fe2+
Iron (III) = Fe3+
Roman numerals:
III 3
VII 7
IV 4
VIII 8
I 1
V 5
IX 9
II 2
VI 6
X 10

26. Ion Size Metals lose electrons
Cations are always smaller than the original atoms.
When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?
Na+ has valence electrons in energy level 2 more pull on valence electrons – smaller ion.

27. Ions Non-metals gain electrons
Anions are always larger than the original atoms.
When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?
More electrons, more repulsion, so electrons “spread out”: larger atom.

28. ISOELECTRIC SERIES N3- O2- F- He Na+ Mg2+ Al3+ Each has 10 electrons.
“Isoelectronic” means ions/atoms with the same number of electrons.
N3- O2- F- He Na+ Mg2+ Al3+
Each has 10 electrons.
This diagram lists the atomic radii of seven nonmetals. An atomic radius is half the distance between the nuclei of two atoms of the same element when the atoms are joined.

29. ISOELECTRIC SERIES N3- O2- F- He Na+ Mg2+ Al3+ Each has 10 electrons.
What is the trend of atomic size for these isoelectric atoms/ions?
largest
smallest
N3- O2- F- He Na+ Mg2+ Al3+
Each has 10 electrons.
This diagram lists the atomic radii of seven nonmetals. An atomic radius is half the distance between the nuclei of two atoms of the same element when the atoms are joined.
Decreasing radius with increasing # of protons. (Due to stronger pull from MORE protons.)

30. Naming Ions NAMING CATIONS (+ metal ions):
04/10/99
NAMING CATIONS (+ metal ions):
Write the name of the metal.
Ca2+ = calcium ion
Li+ = lithium ion
NAMING ANIONS (- non-metal ions):
Root name of element plus “ide”.
Cl- = chloride ion
O2- = oxide ion

31. Naming Ions
04/10/99
Transition Metals (and Pb & Sn) use Roman Numeral for charge
Cobalt (II)
Cobalt (V)
Nickel (III)
Co2+
Co5+
Ni3+

32. Write symbols for these ions:
Titanium (III) ion
Silver ion
Copper (II) ion
Chromium (IV) ion
Nickel (I) ion
Chromium (VI) ion
Ti3+
Ag+
Cu2+
Cr4+
Ni+
Cr6+

33. Chemical Bonds Three basic types of bonds Ionic Covalent Metallic
Between a metal and nonmetal
Attraction between positive and negative ions
Transfer of electrons from one atom to another
Covalent
Sharing of electrons
Two nonmetal atoms
Metallic
Two or more metal atoms
© 2009, Prentice-Hall, Inc.

34. Ionic Bonding
Electrons are transferred from the metal ion (CATION) to a a nonmetal ion (ANION).

35. Ionic Bonding: The Formation of Sodium Chloride
Sodium has 1 valence electron
Chlorine has 7 valence electrons
An electron transferred gives
each an octet
Na: 1s22s22p63s1
Cl: 1s22s22p63s23p5

36. Ionic Bonding: The Formation of Sodium Chloride
This transfer forms ions, each with an octet:
Na+ 1s22s22p6
Cl- 1s22s22p63s23p6

37. Ionic Bonding: The Formation of Sodium Chloride
The resulting ions come together due to electrostatic attraction
(opposites attract):
Na+
Cl-
The net charge on the compound must equal zero

38. Ionic bonding (Li + Cl) Lithium loses 1 electron;
04/10/99
Lithium loses 1 electron;
chlorine gains 1 electron Li Cl
[ Cl ]–
[Li]+

39. Ionic bonding: Mg + O Magnesium loses 2 electrons;
04/10/99
Magnesium loses 2 electrons;
oxygen gains 2 electrons O Mg
[ O ]2–
[Mg]2+

40. Writing Ionic Compound Formulas
Formulas tell how many of each ion is present in a formula. Use subscripts to indicate the number of ions.
The overall charge of a compound must be ZERO.
Fe3+
Cl-
Cl-
Cl-
Iron (III) chloride
The formula is FeCl3

41. Formation of Ionic Compounds
- Each calcium loses 2 electrons;
each chlorine atoms gain 1 electron each
- Overall charge has to be ZERO, so you need TWO chlorides (Cl-) for every one calcium ion Ca2+

42. Writing Ionic Compound Formulas
Example: Beryllium fluoride
1. Write the symbols for the cation and anion, including CHARGES!
Be2+ F- 2 1
2. Check to see if charges are balanced.
Now balanced.
Not balanced!
3. Balance charges , if necessary, using subscripts. Use the criss-cross method to balance subscripts.
= BeF2

43. Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the symbols for the cation and anion, including CHARGES!
Al3+
S2- 2 3
2. Check to see if charges are balanced.
Now balanced.
Not balanced!
= Al2S3
3. Balance charges , if necessary, using subscripts. Use the criss-cross method to balance subscripts.

44. Writing Ionic Compound Formulas
Example: Magnesium Oxide
1. Write the symbols for the cation and anion, including CHARGES!
Mg2+
O2-
2. Check to see if charges are balanced.
Balanced!
= MgO
3. If they’re already balanced, you don’t need to do the criss-cross method. Just write the element symbols. (Use the lowest whole number ratio of subscripts: 1: 1)

45. Writing Ionic Compound Formulas

46. Polyatomic ions are…
Groups of atoms that stay together, have an overall charge, and one name.
Usually end in –ate or -ite
Acetate: CH3COO-
Carbonate: CO32-
Sulfate: SO42-
Sulfite: SO32-
Nitrate: NO3-
Nitrite: NO2-
Phosphate: PO43-
Phosphite: PO33-

47. More Common Polyatomic Ions
The two polyatomic ions ending in –ide:
Hydroxide: OH-
Cyanide: CN-
Ammonium: NH4+ (One of the few positive polyatomic ions)

48. Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the symbols for the cation and anion, including CHARGES!
Mg2+
CO32-
2. Check to see if charges are balanced.
They are balanced!
= MgCO3

49. Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the symbols for the cation and anion, including CHARGES!
( )
Ba2+
NO3- 2 1
2. Check to see if charges are balanced.
Now balanced.
Not balanced!
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance subscripts.
= Ba(NO3)2

50. Writing Ionic Compound Formulas
Example: Ammonium sulfate
( )
1. Write the symbols for the cation and anion, including CHARGES!
NH4+
SO42- 2 1
Now balanced.
2. Check to see if charges are balanced.
Not balanced!
= (NH4)2SO4
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance subscripts.

51. Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the symbols for the cation and anion, including CHARGES!
( )
Zn2+
OH- 1 2
Now balanced.
2. Check to see if charges are balanced.
Not balanced!
= Zn(OH)2
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance subscripts.

52. Writing Ionic Compound Formulas
Example: Aluminum phosphate
1. Write the symbols for the cation and anion, including CHARGES!
Al3+
PO43-
2. Check to see if charges are balanced.
They ARE balanced!
= AlPO4

53. Naming Ionic Compounds
Name the cation first, then anion
CaCl2 = calcium chloride
For transition metals use a Roman numeral in the name:
PbCl2 = lead (II) chloride
Polyatomic anion:
(NH4)2SO4 = ammonium sulfate

54. Practice by writing the name for polyatomic ions Circle the anion and cation in each compound
MgSO4
NH4Cl
AlPO4
Magnesium sulfate
Ammonium chloride
Aluminum phosphate

55. Hints:
If you need more than one polyatomic ion to balance the charges put ( ) around the ion.
If anions end in -ide they are monoatomic [Except OH-, hydroxide & CN-, cyanide]
If anion ends in -ate or –ite, then it is polyatomic

56. Properties of Ionic Compounds
Solid ionic compounds are arranged in a 3-D crystalline pattern = CRYSTAL LATTICE
They have very high melting points
Sodium cations and chloride anions form a repeating three-dimensional array in sodium chloride (NaCl). Inferring How does the arrangement of ions in a sodium chloride crystal help explain why the compound is so stable?

57. Properties of Ionic Compounds
Ionic compounds can conduct an electric current when melted or dissolved in water.
When sodium chloride melts, the sodium and chloride ions are free to move throughout the molten salt. If a voltage is applied, positive sodium ions move to the negative electrode (the cathode), and negative chloride ions move to the positive electrode (the anode). Predicting What would happen if the voltage was applied across a solution of NaCl dissolved in water?