7.3: The Name’s Bond, Chemical Bond
- Page ID
- 31631
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The periodic table tells us something about how different elements react with each other. When two or more atoms combine, they form a bond. A bond is a kind of sharing between atoms that results in their connection. It’s like holding hands with someone you care about. You’re bonded.
Like attractions between people, some chemical bonds are weak, some are strong, but most can be broken under natural conditions. Chemical bonding permits a coming together and coming apart of atoms. In fact, when one bond breaks, another almost always forms. The cool thing about these comings and goings of bonds is that energy is stored or released when bonds form or break, respectively. Organisms break and make chemical bonds as part of the biochemistry of staying alive. We won’t go into the particulars here, but remember that energy is an important part of the discussion of matter; the two go hand in hand.
When two or more atoms bond to each other, a molecule is formed. Molecules may be composed of different atoms, such as carbon dioxide (CO2) or glucose, a simple sugar (C6H12O6). Molecules may also be composed of the same atom, such as oxygen (O2) or nitrogen (N2). These homonuclear molecules are composed of identical atoms that bond to themselves. They are a type of diatomic molecule, meaning they occur in nature as doubles. Diatomic molecules may also be heteronuclear molecules, that is, made of different elements, such as carbon monoxide (CO). A few, such as ozone (O3), represent triatomic molecules. And if all these terms weren’t enough, molecules composed of different atoms are called compounds. Compounds are composed of molecules that are composed of different kinds of atoms (i.e., different elements). So while water (H2O) is a compound, oxygen (O2) is not.
To simplify our discussion, I’ll use the word substance to refer to atoms, molecules, and compounds. Substance refers to all forms of matter with a definite composition. Substances include elements and compounds. You can write the chemical formula for a substance. However, a word of caution is required. The term substance does not include matter with an indefinite composition, such as a solution of something. For solutions chemists use the term mixture. A mixture consists of a collection of two or more atoms or molecules in varying proportions. Seawater is a mixture. The air that you breathe is a mixture. Mixtures can be formed without chemical bonding; there are no chemical reactions involved in their formation. The key point here is that there are different types of atoms, different ways that they hook up, and different ways that they mix. You know, like people.