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

5(B) Use the Periodic Table to identify and explain the properties of chemical families, including alkali metals, alkaline earth metals, halogens, noble gases, and transition metals. 6(E) Express the arrangement of electrons in atoms through electron configurations and Lewis valence electron dot structures. Classification of the Elements Copyright © McGraw-Hill Education

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? Classification of the Elements Copyright © McGraw-Hill Education

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

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. Classification of the Elements Copyright © McGraw-Hill Education

Organizing the Elements by Electron Configuration Classification of the Elements Copyright © McGraw-Hill Education 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.

The s-, p-, d-, and f-Block Elements Classification of the Elements Copyright © McGraw-Hill Education 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.

The s-, p-, d-, and f-Block Elements Classification of the Elements Copyright © McGraw-Hill Education 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.

The s-, p-, d-, and f-Block Elements Classification of the Elements Copyright © McGraw-Hill Education 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.

The s-, p-, d-, and f-Block Elements Classification of the Elements Copyright © McGraw-Hill Education 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.

The s-, p-, d-, and f-Block Elements Classification of the Elements Copyright © McGraw-Hill Education 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.

Classification of the Elements Copyright © McGraw-Hill Education Electron Configuration and the Periodic Table EVALUATE THE ANSWER The relationships between electron configuration and position on the periodic table have been correctly applied. Use with Example Problem 1. Problem Strontium, which is used to produce red fireworks, has an electron configuration of [Kr]5s 2. 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. KNOWNUNKNOWN Electron configuration = [Kr]5s 2 Group = ? Period = ? Block = ? SOLVE FOR THE UNKNOWN For representative elements, the number of valence electrons can indicate the group number. The s 2 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 5s 2 indicates that strontium is in period 5.

Classification of the Elements Copyright © McGraw-Hill Education 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?