• The electron level arrangement of atoms are an important factor in the physical and chemical behavior of the elements.

Valence Electrons
electrons in the outermost energy level of an atom

Group Numbers 1A – 8A
designations at the top of each group of representative elements that indicates the number of valence electrons

What is one of the most important factors in the physical and chemical behavior of the elements?
 

Practice Problems Answer the following questions:

1. What are valence electrons?

2. Using the Periodic Table, write the Group Numbers and the number of valence electrons for the following elements: . a) sodium b) sulfur c) silicon d) indium .

3. What is the group number, name, and symbol of the element with atoms that have five valence electrons in the 3rd energy level?

Electron-Dot Symbols (a.k.a. Lewis Structures)
the representation of an atom that shows valence electrons as dots around the symbol of an element

1-4 valence electrons are arranged by single dots (added clockwise)
more than 4 valence electrons & dots begin to pair up.

What electrons are depicted in Electron-Dot Symbols?
 

Practice Problems Answer the following questions:

1. Write the electron-dot symbol for each of the following elements: . a) bromine b) iodine c) indium d) argon .

2. What is the electron-dot symbol for phosphorus? . What group is it in?

3. What is the electron-dot symbol for antimony (Sb*)? . What group is it in? . * Sb from stibium, the ancient name for antimony sulfide, Sb2S3.

Atomic Size measured by the Atomic Radius the distance from the nucleus to the valence electrons On the periodic table, atomic size tends to Increase going down the column Decrease going across the rows from left to right.

Ionization Energy
the energy needed to remove the least tightly bound electrons from an atom in the gaseous state

On the periodic table, ionization energy tends to
  decrease going down the column and
  increase going across the rows from left to right.

Ionization energy is low for metals, high for non-metals.

Electronegativity
Ability of an atom to attract electrons when the atom is in a compound

Trends in electronegativity are equivalent to ionization energy.

What are the trends in Atomic Size, Ionization Energy, & Electronegativity?
 

Practice Problems Answer the following questions:

1. What is the atomic radius?

2. Do the valence electrons get closer to the nucleus or farther away as you go down the Group?

3. Do the valence electrons get closer to the nucleus or farther away as you go across the Period from left to right?

4. What is ionization energy?

5. Indicate the element in each set that has the higher ionization energy and explain your choice: . a) H, K, or Na b) Mg, Si, or Cl c) F, N, or C .

6. Explain the relationship between the size of the atom and its ionization energy.

7. Arrange Sn, I, and Sr in order of increasing ionization energy.

8. What is Electronegativity?

9. Arrange Sn, I, and Sr in order of increasing atomic radius.