1. Warm-Up 10/17/2016
Place the following elements in increasing electronegativity and increasing atomic size
K, Br, Fe, Cs, Se

2. Unit 3
Bonds - Chemical Bonds

3. Valence Electrons
What are Valence Electrons?
Valence electrons are the electrons on the outermost energy level
This can be determined by either the electron configuration or by where the element is located on the periodic table.

4. Quick Way to find Valence Electrons
Look at the group number in the periodic table for each family
Consider Li
Li is in group 1
Take the last digit in the group number and that tells the number of valence electrons
Thus, Li has 1 valence electron

5. Quick Way for Valence E-
Consider Be
Be is in group 2
What is the last digit in the group number? 2
Thus, Be has 2 valence electrons

6. Quick Way for Valence E-
Remember: It is the last digit in the group number
Consider B
B is in group 13
What is the last digit in the group number? 3
Thus, Be has 3 valence electrons

7. Quick Way for Valence E-
Consider C
C is in group 14
What is the last digit in the group number? 4
Thus, C has 4 valence electrons
Remember: It is the last digit in the group number

8. Quick Way for Valence E-
Remember: It is the last digit in the group number
Consider N
N is in group 15
What is the last digit in the group number? 5
Thus, N has 5 valence electrons

9. Quick Way for Valence E-
Consider O
O is in group 16
What is the last digit in the group number? 6
Thus, O has 6 valence electrons
Remember: It is the last digit in the group number

10. Quick Way for Valence E-
Consider Cl
F is in group 17
What is the last digit in the group number? 7
Thus, Cl has 7 valence electrons
Remember: It is the last digit in the group number

11. Quick Way for Valence E-
Remember: It is the last digit in the group number
Consider Rn
Rn is in group 18
What is the last digit in the group number? 8
Thus, Rn has 8 valence electrons
**Helium is an exception to this rule; it only has 2 electrons!**

12. Practice finding Valence ElectronsNa Ge In Ra I Cl Ne He P B

13. Find the valance electrons from electronic configuration
1s22s22p63s2
 1s22s22p63s23p1
1s22s22p63s23p3
1s2 2s2 2p6 3s2 3p6 4s1
1s2 2s22p63s23p64s23d104p5

14. Element Quiz - 4
Which element has an atomic number of 36? How many electrons this element has?
Write down the mass number, number of protons and number of neutrons for Rubidium?
Which element has 40 protons, and 51 neutrons?
Write down the symbol for the element Yttrium. Mark its atomic number and mass number with its symbol?
Which element has the symbol ‘Sr '?

15. Properties of Ionic Compounds
Hard
Form Crystal solids not molecules
Good insulators
High melting points and Boiling points
Conducts electricity when dissolved in water or as a liquid
Ionic Solids do not conduct electricity
∆EN > 1.7

17. Octet Rule
The Octet Rule states that all atoms want to achieve a noble gas configuration in order to become chemically stable
An Ion is an element that either gains or loses electrons

18. Exception Octet Rule
Generally this means all atoms strive to have eight (8) valence electrons
However, a few elements will become like Helium and have two (2) valence electrons

19. Metals lose electrons; nonmetals gain electrons
Effect of Octet Rule
Metals lose electrons; nonmetals gain electrons
When electrons are gained or lost, the element’s number of electrons changes
Na = 11 e-; 1s22s22p63s1
Na+ = 10 e-; 1s22s22p6

20. Chemical Symbols for Ions
When an atom gains or loses electrons, the correct way to write the chemical symbol is the following:
1) Write the symbol for the atom
2) Determine the net change in electrons

21. Chemical Symbols for Ions
3) If electrons are gained, the atom becomes more negative. If electrons are lost, the atom becomes more positive.

22. 4) Write the symbol of the element.
5) Write the charge of the particle in the upper right hand corner after the element
Example: Oxygen gains 2 e-
Lithium loses 1 e-

23. Write Symbols for the following:
1. A sulfur atom that gains 2 e-
2. A sodium atom that loses 1 e-
3. A nitrogen atom that gains 3 e-
4. A magnesium atom that loses 2 e-
Identify the anions and cations above
Determine how many protons and electrons each atom has

24. Ionic Charges of Elements
The following families take the following charges in IONIC COMPOUNDS:
Group 1: +1
Group 2: +2
Group 13: +3
Group 14: 4 24

25. Ionic Charges of Elements
Group 15: -3
Group 16: -2
Group 17: -1
Group 18: 0 *do NOT form compounds
Groups 3-12 can take different charges 25

26. Determine the charge of the following in ionic compounds
1. Na
2. Cl
3. S
4. P
5. Ra
6. Ca
7. I
8. Fr
9. Al
10. O 26

27. Determine the Ionic Charge of the following
11. Sr
12. Te
13. N
14. Mg
15. Se

28. Compounds
Compounds are a combination of at least two elements that act as one unit
Compounds have separate identities different from their component elements

29. Compounds
When a compound forms it causes a chemical bond to occur.
A chemical bond -is the force that holds two atoms together
This is the result when electrons are gained, lost, or shared between atoms

30. Types of Compounds If electrons are shared, a COVALENT BOND results
If electrons are gained or lost, an IONIC BOND results
If valence electrons are moving freely through the metals lattice a METALLIC BOND results

31. Types of Compounds Continued
Covalent bonds form ONLY between NONMETALS
Example: CO2, SO2
Covalent bonds form molecular compounds
Molecular compounds have low melting and boiling points

32. Types of Compounds Continued
Ionic bonds form between METALS & NONMETALS only
Example: NaCl, MgCl2
Ionic bonds form ionic compounds which stay together due to the electrostatic attraction between the cat-ion and an-ion
Ionic compounds are usually crystalline solids at room temperature

33. Metallic Bonds form between TWO METALS
Example: metal alloys (Brass, Steel)
Metallic Bonds result in extremely strong compounds, which conduct electricity and heat very well
Brass is made with Zinc and Copper
Steel is Carbon and Iron
Metallic bonding is utilized for its conductive properties to help transfer electricity throughout a house via copper wiring.

34. What are the Charges of the ions of the following elements?Ca Br Sr B Se

35. Draw the Bohr diagram to represent the ionic bonds
K,Cl
Ca, Cl
Ba, Cl

36. Chemical Formulas
Chemical Formulas show the kinds and number of each atom present
The small numbers written below a symbol are called SUBSCRIPTS
Subscripts show the number of each atom present
Metals are written first in the formula