Section 2: Classification of the Elements Elements are organized into different blocks in the periodic table according to their electron configurations. K What I Know W What I Want to Find Out L What I Learned

Essential Questions Why do elements in the same group have similar properties? Based on their electron configurations, what are the four blocks of the periodic table? Copyright © McGraw-Hill Education Classification of the Elements

Vocabulary Review valence electron Classification of the Elements Copyright © McGraw-Hill Education

Organizing the Elements by Electron Configuration Recall electrons in the highest principal energy level are called valence electrons. All group 1 elements have one valence electron. Copyright © McGraw-Hill Education Classification of the Elements

Organizing the Elements by Electron Configuration Group 2 elements have two valence electrons. The number of valence electrons for elements in groups 13–18 is ten less than their group number. The energy level of an element’s valence electrons indicates the period on the periodic table in which it is found. Classification of the Elements Copyright © McGraw-Hill Education

The s-, p-, d-, and f-Block Elements The shape of the periodic table becomes clear if it is divided into blocks representing the atom’s energy sublevel being filled with valence electrons. Copyright © McGraw-Hill Education Classification of the Elements

The s-, p-, d-, and f-Block Elements s-block elements consist of group 1 and 2, and the element helium. Group 1 elements have a partially filled s orbital with one electron. Group 2 elements have a completely filled s orbital with two electrons. Copyright © McGraw-Hill Education Classification of the Elements

The s-, p-, d-, and f-Block Elements Groups 13–18 fill the p orbitals. In group 18, both the s and p orbitals of the period’s principal energy level are completely filled. Copyright © McGraw-Hill Education Classification of the Elements

Interactive Table – Noble Gas Electron Configuration Concepts in Motion Classification of the Elements Copyright © McGraw-Hill Education

The s-, p-, d-, and f-Block Elements The d-block contains the transition metals and is the largest block. There are exceptions, but d-block elements usually have filled outermost s orbitals, and filled or partially filled d orbitals. The five d orbitals can hold 10 electrons, so the d-block spans ten groups on the periodic table. Copyright © McGraw-Hill Education Classification of the Elements

The s-, p-, d-, and f-Block Elements The f-block contains the inner transition metals. f-block elements have filled or partially filled outermost s orbitals and filled or partially filled 4f and 5f orbitals. The 7f orbitals hold 14 electrons, and the inner transition metals span 14 groups. Copyright © McGraw-Hill Education Classification of the Elements

Electron Configuration and the Periodic Table SOLVE FOR THE UNKNOWN For representative elements, the number of valence electrons can indicate the group number. The s2 indicates the strontium’s valence electrons fill the s sublevel. Thus, strontium is in group 2 of the s-block. The number of the highest energy level indicates the period number. The 5 is 5s2 indicates that strontium is in period 5. Use with Example Problem 1. Problem Strontium, which is used to produce red fireworks, has an electron configuration of [Kr]5s2. Without using the periodic table, determine the group, period, and block of strontium. Response ANALYZE THE PROBLEM You are given the electron configuration of strontium. EVALUATE THE ANSWER The relationships between electron configuration and position on the periodic table have been correctly applied. KNOWN UNKNOWN Electron configuration = [Kr]5s2 Group = ? Period = ? Block = ? Copyright © McGraw-Hill Education Classification of the Elements

Review Essential Questions Why do elements in the same group have similar properties? Based on their electron configurations, what are the four blocks of the periodic table? Copyright © McGraw-Hill Education Classification of the Elements