1. Mr. Conkey Physical Science Ch. 6
Chemical Bonds
Mr. Conkey Physical Science Ch. 6

2. Stable Electron Configurations
When the highest energy level of an atom is filled with e−’s, it is stable and unlikely to react
Group 8 all have stable e− configurations (including He)
Chemical properties depend on the # of valence e−’s
Electron dot diagram – a model of an atom in which each dot represents a valence e−

3. Electron Dot Diagrams for some Group Elements

4. Ionic Bonds (e− Donors and e− Acceptors)
Elements with incomplete sets of valence e−’s tend to react
Some elements achieve a stable electron configuration through the transfer of electrons between atoms
Example of electron transfer:
Full Octet (now stable)
e− donor
e− acceptor
Donated e− (also now stable
Chlorine needs to gain one electron to be stable (See nearest Noble Gas, Argon); Sodium needs to lose one electron to be stable (to be like nearest Noble Gas, Neon)

5. Formation of Ions
Ions – form when an atom gains or loses an electron and the number of protons and electrons become ≠
The charge on an ion is shown by a plus or minus sign (i.e. Na+ and Cl ‾ )
Cation – an ion with a positive charge (+)
Anion – an ion with a negative charge ( ‾ )

6. Ionization Energy
Cations form when e−’s gain enough energy to leave the atoms!
The energy allows for the e−’s to overcome the attractive forces of the protons in the nucleus
Ionization energy – the amount of energy needed to eject an e−

7. Ionic Compounds Ionic compounds – compounds that contain ionic bonds
Chemical formula – a notation that shows the ratio of the atoms/ions of elements in a compound as well as what elements are in the compound
Example: MgCl₂
Charges appear after electron transfer. Since Mg has a +2 charge, it needs to ionically bond to two Chlorine atoms (-1 charge)

8. Properties of Ionic Compounds
Ionic compounds have high melting points, good conductors of electric current (when melted), and are brittle
Ionic compounds tend to shatter when struck because the ions move from their fixed positions and like charges repel each other causing them to shatter

9. Covalent Bonds (sharing of e−’s)
Nonmetals bond together using covalent bonds (two atoms sharing a pair of valence e−’s) and form a molecule
Two Hydrogen atoms share their valence e−’s to form a stable e− configuration
Molecule – a neutral group of atoms joined together by one or more covalent bonds
H₂ Molecule

10. Molecules and Multiple Covalent Bonds
Attractions between the shared e−’s and the protons in the nucleus hold atoms together in covalent bonds
The amount of covalent bonds needed in a molecule depends on the # of valence e−’s of the atoms

11. Some Common Cations and Anions

12. Metallic Bonds
Metallic bond – the attraction between a metal cation and the shared e−’s surrounding it
Metallic bonds are relatively strong
Electric current and malleability are due to the ability for the e−’s to move
Pool of e−’s allow for good electric conductivity
Cation and e−’s shifting allow for malleability

13. Alloys
Alloy – a mixture of two or more elements (at least one has to be a metal!)
Cu alloys:
Bronze (Cu and Sn); two soft metals when mixed are much harder/stronger
Brass (Cu and Zn); softer than bronze and easier to shape and shinier
Brass
Bronze

14. You Made it, its the end of the notes!!!! WOOHOOOOOO!!!!!!!

15. Now the Battle of the Finals Begins!