Page 179 - Chemistry--atom first

Chapter 3 | Electronic Structure and Periodic Properties of Elements 169
Solution
The family names are as follows: (a) halogen
(b) alkaline earth metal
(c) alkali metal
(d) chalcogen
Check Your Learning
Give the group name for each of the following elements: (a) krypton
(b) selenium
(c) barium
(d) lithium
Answer: (a) noble gas; (b) chalcogen; (c) alkaline earth metal; (d) alkali metal
In studying the periodic table, you might have noticed something about the atomic masses of some of the elements. Element 43 (technetium), element 61 (promethium), and most of the elements with atomic number 84 (polonium) and higher have their atomic mass given in square brackets. This is done for elements that consist entirely of unstable, radioactive isotopes (you will learn more about radioactivity in the nuclear chemistry chapter). An average atomic weight cannot be determined for these elements because their radioisotopes may vary significantly in relative abundance, depending on the source, or may not even exist in nature. The number in square brackets is the atomic mass number (and approximate atomic mass) of the most stable isotope of that element.
3.7 Molecular and Ionic Compounds
By the end of this section, you will be able to:
• Define ionic and molecular (covalent) compounds
• Predict the type of compound formed from elements based on their location within the periodic table
• Determine formulas for simple ionic compounds
In ordinary chemical reactions, the nucleus of each atom (and thus the identity of the element) remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons, and form electrically charged particles called ions (Figure 3.40).