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Section 6.2

Explore why elements in the same group share properties and learn about the 4 blocks in the periodic table based on electron configuration. Discover how valence electrons and energy levels play a crucial role in classifying elements. Practice problem-solving without the periodic table.

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Section 6.2

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  1. Section 6.2 Classification of the Elements

  2. Objectives • Explain why elements in the same group have similar properties. • Identify the 4 blocks of the periodic table based on electron configuration.

  3. The Periodic Table Period 1 hydrogen 1s1 Period 2 lithium 1s22s1 Period 3 sodium 1s22s22p63s1 Period 4 potassium 1s22s22p63s23p64s1 What do these elements have in common?

  4. Classification by valence electrons • Atoms of the same group have similar properties because they have the same number of valence electrons. • The number (in the group number) that accompanies the “A” designations tells you the number of valence electrons for that element. • There is one exception . . .

  5. See p. 183 Fig. 7 Classification by valence electrons

  6. Classification by energy level • The period number corresponds to the energy level of the valence electrons. • Valence electrons will always be in the highest energy level. • Where are the valence electrons for Ga? • How many valence electrons does Ga have?

  7. Classification by “Block” • The Periodic Table can be viewed as arranged into blocks. • Each block corresponds to the sublevel in which the outermost electrons are located.

  8. Classification by “block”

  9. Classification by “Block” • s block: groups IA (electron configuration ends with s1) & IIA (electron configuration ends with s2 ) • p block: groups IIIA to VIIIA (electron configurations ending with p1, p2, p3, p4, p5, & p6 respectively) • All p block elements have a filled s orbital • d block: transition metals • All d block elements have a filled s orbital BUT . . .

  10. Energy level for d orbitals is n -1 • (Remember n is the principal energy level or period number) • Example: Fe (atomic # 26) is [Ar] 4s23d6

  11. Classification by “Block” • f block: Inner transition elements • s sublevel is filled • electron configurations end with n-2 f1-14 (Note: the energy level for f orbitals is n-2) • f sublevel does not “fill” with electrons in a predictable way

  12. Practice Problems • Without using the periodic table, determine the group, period, and block of an atom of this configuration: [Kr] 5s2 4d9 • Write the electron configuration for a group 2A element in period 5. • What elements have the following valence electron configuration: s2 p1?

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