Unit+4

By: Megan, Jenna, Kirsten, Hailey, Carly, and Julianna   **Trends in the periodic table:**
 * ☺ UNIT 4 ☺ **

1. Atomic radius: Within a group increases as one moves vertically down the periodic table, and decreases moving right across the periodic table.

2. Shielding effect: A decrease in the attraction of the other electron to the positively charged nucleus (valence electrons). It increases as one moves vertically down the periodic table. It also remains constant as you move right across the periodic table, because the electrons aren't being added to a new s energy level.

3. Electronegativity: This is how strong the bonds are within a compound. Decreases as you move down the periodic table, because the energy levels are growing, and it increases as you move right across the periodic table, because the protons are added to the nucleus allowing for more electrons.

4. Ionization energy: Is the energy required for removing an electron from an element. it decreases going vertically down the periodic table. It also increases moving horizontally right across the periodic table.

5. Electron Affinity: A measure of the energy change that occurs as an electron is added to an atom. It has the same trends as electronegativity for the same reasons.


 * Periodic Table Groupings: ** 

• Group 1A on the periodic table are alkali metals, other than hydrogen • Group 2A is comprised of the alkaline earth metals • Group 3B, 4B, 5B, 6B, 7B, 8B, 1B, and 2B are all transition metals → also known as the d-subshell • Group 8A are the noble gases • Group 7A consists of halogens • The lanthanide series are the elements in the F1 orbital. • An actinide series are the elements in the F2 orbital. • Non Metals are boron, carbon, nitrogen, oxygen, silicon, phosphorus, sulfate, acetate, selenium, and tellurium • The metals are aluminum, gallium, germanium, indium, tin, antimony, thallium, lead, bismuth, and polonium • The 7 diatomic elements are= Hydrogen, nitrogen, oxygen, flourine, chlorine, iodine, and bromine.



 **Measurements:**

Mole: base comparison of all types of elements Amu: measurement of one element or atom Grams: measurement of a mole of atoms

amu (atomic mass units): isotopes are 1 atom of an element sample Grams (molar mass) : 6.022 x 10^23 atoms, equals the number of grams in one mol. Example: 1.00794 H / 1 mol = 6.022 x 10^23 atoms H

**Characteristics of moles:**

1. An equal comparison for all elements. 1 mol = 6.022 x 10^23 atoms, no matter what element 2. We measure "g" to get to a mole 3. An atom=a single element 4. A molecule=multiple elements grouped

• Avogardo's Number is the number of particles of one mole of a pure substance →6.022 x 10^23

• Atomic mass is expressed in atomic mass units, or amu

• Use amu when measuring a single atom

• Grams are used when there is more than one atom

**Practice Problems:**

1. What 3 properties of an element decrease as you go down a group? Answer: Ionization energy, Electronegativity, and Electron Affinity → because these properties are actually the highest in the upper region of the table.

2. The only group that does not have a value for electronegativity is the Answer: Noble Gases → because they don’t want to bond with anything.

3. What is the atomic mass of 25.27 moles of Helium? Answer: 101.1 amu → 25.27 mol X (4.00260 amu/1 mol) = 101.1 amu

4. How many atoms are in 155 mol of arsenic? Answer: 155/1 X 6.022x 1023 atoms = 9.33 x 1025