1. 4. Bonding of Atoms and Formation of Ions

2. Pure Substances-review
ELEMENTS
COMPOUNDS
only contain one type of atom
contain two or more types of atoms that have combined chemically (bonded) to form a new substance.
if you have a few atoms or billions of atoms, the ratio of atoms is the same throughout the compound
ratio is always 2:1 in this compound
sample of monatomic element
sample of diatomic element (atoms bonded as molecules)
2 different types of atoms bonded
sample of a compound

3. Bonding
Atoms will exchange or share enough valence electrons to fill their outer energy level to become stable.
Atoms which share or exchange electrons stay together. This is called bonding.
New bonds are formed (so new substances are made) when substances collide and chemically react.

4. Full valence = stability
When the outer valence of an atom is full of electrons, they are stable.
The noble gases have a full valence and are stable. Because of this they do not try to form bonds with other substances. We say that they are non-reactive or inert.

5. Sort Activity Sort the compounds into two groups.
Identify the characteristics of each group.

6. Compounds MATTER IMPURE SUBSTANCES PURE SUBSTANCES ELEMENTS COMPOUNDS
METALS
(Na, Ca, Fe, Ni)
NONMETALS
(S, He, F2, O2, N2)
IONIC
Metal + Nonmetal
MOLECULAR
Nonmetals only
formed from the attraction (bonding) of oppositely charged ions
formed from the attraction (bonding) of molecules

7. Patterns in compound formation
Metals donate all valence electrons to nonmetals to form ionic compounds.
Nonmetals share valence electrons with other non-metals to form molecular compounds.
Atoms DO NOT exchange protons.
How atoms bond
MOLECULAR Compounds
Nonmetal + Nonmetal
SHARE electrons
IONIC Compounds
Metal + Nonmetal
EXCHANGE electrons

8. Formation of Ions

9. Ionic Bond Formation
When non-metals and metals collide with enough energy each other, the metal gives the non-metal it’s valence electrons and they become oppositely charged ions with full valence shells.

10. Bohr model: formation of ionic bond
METAL
donates valence e-
+charge
cation
NON-METAL
accepts e-
-charge
anion
oppositely charged ions attract and
ionic compound forms

11. Lewis model: formation of ionsNa + Cl
x x x Na x Cl
x x x x

12. Lewis model: formation of ions2+ Mg Cl
x x x Cl
x x x Mg x x Cl
x x x Cl
x x x x

13. Changes in electrons and ionic charges
Group
number
Atomic number
Protons
(stays the same)
Electrons
(in neutral atom)
(in ion)
Charge
Lost or gained # electrons 1 3
+ + +
_ _ _
_ _ +1
lost 1 2 4
_ _ _ _ +2
lost 2 15 7
_ _ _
_ _ -3
gained 3 17 9 _ -1
gained 1
...

14. Periodic table and patterns of ion formation
Group 1 2 13 14 15 17 18
#valence e- 3 4 5 6 7 8
charge +1 +2 +3 NA -3 -2 -1
change in e-
loses 1
loses 2
loses 3
shares
gains 3
gains 2
gains 1
stable
type of ion
cation
anion
type of element
metal
non-

15. Know the charges of ions formed by the elements in groups 1-2 and 13-18

16. Practice
Ion patterns in periodic table
All about ions
Charges of ions