chemistry of compounds

types of compounds

There are two basic types of compounds that differ in the nature of the bonds that hold their atoms or ions together. They are covalent and ionic compounds. Both types are described below. Click image to the left or use the URL below. URL: Covalent compounds consist of atoms that are held together by covalent bonds. These bonds form between nonmetals that share valence electrons. Covalent compounds exist as individual molecules. Water is an example of a covalent compound. Ionic compounds consist of ions that are held together by ionic bonds. These bonds form when metals transfer electrons to nonmetals. Ionic compounds exist as a matrix of many ions, called a crystal. Sodium chloride (table salt) is an example of an ionic compound.

same elements different compounds

Look at the Figure 1.2 of water (H2 O) and hydrogen peroxide (H2 O2 ), and read about these two compounds. Both compounds consist of hydrogen and oxygen, but they have different ratios of the two elements. As a result, water and hydrogen peroxide are different compounds with different properties. If youve ever used hydrogen peroxide to disinfect a cut, then you know that it is very different from water! Q: Read the Figure 1.3 about carbon dioxide (CO2 ) and carbon monoxide (CO). Both compounds consist of carbon and oxygen, but in different ratios. How can you tell that carbon dioxide and carbon monoxide are different compounds? Carbon Dioxide: Every time you exhale, you release carbon dioxide into the air. Its an odorless, colorless gas. Car- bon dioxide contributes to global climate change, but it isnt directly harmful to hu- man health. Carbon Monoxide: Carbon monoxide is produced when matter burns. Its a colorless, odorless gas that is very harmful to human health. In fact, it can kill people in minutes. Because you cant see or smell carbon monoxide, it must be detected with an alarm.

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what are compounds

A compound is a unique substance that forms when two or more elements combine chemically. Compounds form as a result of chemical reactions. The elements in compounds are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions that share or transfer valence electrons. Click image to the left or use the URL below. URL: Water is an example of a common chemical compound. As you can see in the Figure 1.1, each water molecule consists of two atoms of hydrogen and one atom of oxygen. Water always has this 2:1 ratio of hydrogen to oxygen. Like water, all compounds consist of a fixed ratio of elements. It doesnt matter how much or how little of a compound there is. It always has the same composition. Q: Sometimes the same elements combine in different ratios. How can this happen if a compound always consists of the same elements in the same ratio? A: If the same elements combine in different ratios, they form different compounds.

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instructional diagrams

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questions

all compounds consist of a fixed ratio of elements.

-->  a. true

b. false

covalent compounds are compounds that

a) consist only of nonmetallic elements.

b) have atoms that share electrons.

c) exist as individual molecules.

-->  d) all of the above

water is an example of a covalent compound.

-->  a. true

b. false

ionic compounds are compounds that

a) consist only of metallic elements.

-->  b) have atoms that transfer electrons.

c) exist as individual ions.

d) all of the above

carbon dioxide is an example of an ionic compound.

a. true

-->  b. false

diagram questions

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