OBJECTIVES: By the end of class, students will be able to. SWBAT find the number of shells and number of valence electrons for the different elements.

Transcription

1 7 th Grade Science Name: Unit: Matter and Periodic Table Lesson: Atoms 4 Valance Elections I OBJECTIVES: By the end of class, students will be able to SWBAT find the number of shells and number of valence electrons for the different elements. DO NOW Date: Homeroom: 1. Label the information below. 2. What does the atomic number represent? or 3. What does the atomic mass represent? + 4. How would you find the number of neutrons in an atom? 5. Atomic Number: 6. Atomic Mass: 1

2 REVIEW # of = Atomic Number # of = Atomic Number i. Therefore, # of = # of # of = Atomic Mass Atomic Number # of Protons + # of Neutrons = Find the number of protons, electrons, and neutrons in an element using the periodic table 2

3 Class Notes 1. Periods: Each is called a. a. The elements in each period have the number of shells. i. Shells? 1. Shells are the around the nucleus where the are found. 2. Each shell can only hold a certain number of electrons. a. The 1 st shell can hold up to two electrons, the 2 nd shell can hold up to eight electrons, the 3 rd shell can hold up to 18, and 4 th shell can hold up to 32, and so on. i. 1 st shell = electrons ii. 2 nd shell = electrons iii. 3 rd shell = electrons iv. 4 th shell = electrons 1 st Period = 1 Shell 2 nd Period = 2 Shells 3 rd Period = 4 th Period = 4 Shells = 5 Shells 6 th Period = 6 Shells 7 th Period = 7 Shells 3

4 2. Groups: Each is called a group or. a. Each element in a group has the same number of in their outer orbital, also known as. b. The electrons in the outer shell are called electrons. i. You can check to see if you are correct in your electron count, if the electrons add up to the #. 1 Electron 8 2 Electrons Skip Transition Metals When Counting Electrons 3. Transition Metals: Transition Metals have slightly different rules for and (outer)electrons. a. We are going to count transition metals as groups. i. Groups will be counted as 1-8, not 1-18 (skipping the 10 Transition element groups). ii. This is something you will learn about in High School Chemistry. 4. Exception to the valence electron rules: 1. Transition Metals 2. Helium, He, only has two valence electrons. 4

5 GUIDED PRACTICE : Determine the number of shells and the number of valence (outer) electrons for SKIP Carbon, C a. How many shells? 2 nd period = shells. b. How many valence electrons? 4 th Group = valence electrons c. What it looks like. 2 nd Period = 2 shells C 4th Group = 4 valence electrons 2. Sodium, Na a. How many shells? period = shells 1 st Group = 1valence electron b. How many valence electrons? group = valence electron. c. What it looks like. Remember to fill the shells before you move on, exception the last electron may go into another shell depending on the group. 1 st shell = electrons 2 nd shell = electrons 3 rd shell = electrons 3 rd Period = 3 shells 5

6 1 2 SKIP Neon, Ne a. Number of shells? b. Number of valence electrons? 4. Hydrogen, H a. Number of shells? b. Number of valence electrons? 6

7 5. Beryllium, Be a. Number of shells? b. Number of valence electrons? INDEPENDENT PRACTICE 1. How many electrons can each shell hold? 1 st 2 nd 3 rd 4 th 2. What term is used for the outer most electrons? 3. Sulfur, S Number of shells? Number of valence electrons? Draw it 7

8 4. Sodium, Na Number of Shells? Number of valence electrons? Draw it 5. Helium, He (don t forget about the exception) Number of shells? Number of valence electrons? Draw it 8

9 Science 7 Name: SKILL SNAPSHOT Date: Atoms.4 Homeroom: Quick Notes: Like A Scholar? Yes No Redo? Yes No Directions: Determine the number of shells and the number of valence (outer) electrons for the following elements. 1. Magnesium, Mg a. Number of shells? b. Number of valence electrons? 2. Chlorine, Cl a. Number of shells? b. Number of valence electrons? 9

10 3. Boron, B a. Number of shells? b. Number of valence electrons? 4. Lithium, Li Number of shells? Number of valence electrons? Draw it 5. Nitrgon, N Number of shells? Number of valence electrons? Draw it 10