Pairs of metal atoms may share electrons, as in Hg22+. QUESTION: Which of the following pairs atoms is most likely to form an ionic bond? A. C and H, B. Ca and H, C. Hg and Hg Ionic bonding tends to occur between a metallic element and a nonmetallic element. Atoms of metallic elements tend to readily lose electrons and become positively charged, whereas atoms of nonmetallic element tend to gain electrons and become negatively charged. Between two nonmetal atoms, electron sharing, “covalent bonding” is more likely to occur. Among atoms of metallic element, electrons are loosely held and delocalized: “metallic bonding” Pairs of metal atoms may share electrons, as in Hg22+. SCRIPT: Which of the following pairs atoms is most likely to form an ionic bond? A. C and H, B. Ca and H, C. Hg and Hg PAUSE Ionic bonding tends to occur between a metallic element and a nonmetallic element. Atoms of metallic elements tend to readily lose electrons and become positively charged, whereas atoms of nonmetallic element tend to gain electrons and become negatively charged. Among the choices given, the only metal-nonmetal pair is choice B. Calcium is a metal, and hydrogen is a nonmetal. The calcium atom becomes calcium ion. CALLOUT “Ca2+” And the hydrogen atom becomes a hydride ion CALLOUT “H-” Between two nonmetal atoms, as in choice A, electron sharing,… or covalent bonding HIGHLIGHT is more likely to occur. Carbon and hydrogen are more likely to share electrons. Among atoms of metallic elements, electrons are loosely held and are more or less free to move about among the atoms. We say that the electrons are delocalized among the atoms. What we have among metallic atoms is called “metallic bonding” However, pairs of metal atoms may share electrons, as in the mercurous ion. HIGHLIGHT Hg22+. CALLOUT “mercurous” This mercury atoms in this ion are sharing electrons, but the pair as a whole is missing two electrons. That’s why it has a +2 charge. This diatomic ion is also called mercury one. CALLOUT “mercury(I)” That’s mercury followed by the roman numeral one in parentheses. The is no naturally-occurring monatomic mercury ion has a charge of +2. It’s called mercury two. There is no naturally-occurring monatomic mercury ion with a charge of +1. What’s called mercury one, is diatomic, … with a charge of +2. It’s called mercury one because it’s as if each mercury has a charge of –1. CONTINUED ON NEXT SLIDE

Here’s a periodic table to remind you where the metals and nonmetals are located in the periodic table. The metallic elements are shown here highlighted in red. The nonmetallic elements are highlighted in blue. And the metalloids are not highlighted. Here’s calcium… CLICK It’s a metal Here’s hydrogen CLICK It’s a nonmetal Here’s carbon And here’s mercury CLICK It’s a metal PAUSE END RECORDING

Video ID: 1-18-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08