molecular compounds

naming and writing formulas for covalent compounds

To name simple covalent compounds, follow these rules: Start with the name of the element closer to the left side of the periodic table. Follow this with the name of element closer to the right of the periodic table. Give this second name the suffix -ide. Use prefixes to represent the numbers of the different atoms in each molecule of the compound. The most commonly used prefixes are shown in the Table 1.1. Number 1 2 3 4 5 6 Prefix mono- (or none) di- tri- tetra- penta- hexa- Q: What is the name of the compound that contains three oxygen atoms and two nitrogen atoms? A: The compound is named dinitrogen trioxide. Nitrogen is named first because it is farther to the left in the periodic table than oxygen. Oxygen is given the -ide suffix because it is the second element named in the compound. The prefix di- is added to nitrogen to show that there are two atoms of nitrogen in each molecule of the compound. The prefix tri- is added to oxygen to show that there are three atoms of oxygen in each molecule. In the chemical formula for a covalent compound, the numbers of the different atoms in a molecule are represented by subscripts. For example, the formula for the compound named carbon dioxide is CO2 . Q: What is the chemical formula for dinitrogen trioxide? A: The chemical formula is N2 O3 .

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properties of covalent compounds

The covalent bonds of covalent compounds are responsible for many of the properties of the compounds. Because valence electrons are shared in covalent compounds, rather than transferred between atoms as they are in ionic compounds, covalent compounds have very different properties than ionic compounds. Many covalent compounds, especially those containing carbon and hydrogen, burn easily. In contrast, many ionic compounds do not burn. Many covalent compounds do not dissolve in water, whereas most ionic compounds dissolve well in water. Unlike ionic compounds, covalent compounds do not have freely moving electrons, so they cannot conduct Name of Compound(Chemical For- mula) Sodium chloride (NaCl) Lithium fluoride (LiF) Type of Compound Boiling Point ( C) ionic ionic 1413 1676 Q: The two covalent compounds in the table are gases at room temperature, which is 20 C. For a compound to be a liquid at room temperature, what does its boiling point have to be? A: To be a liquid at room temperature, a covalent compound has to have a boiling point higher than 20 C. Water is an example of a covalent compound that is a liquid at room temperature. The boiling point of water is 100 C.

what are covalent compounds

Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds. In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction between the shared electrons and the positive nuclei of both atoms holds the atoms together in the molecule. A molecule is the smallest particle of a covalent compound that still has the properties of the compound. The largest, most complex covalent molecules have thousands of atoms. Examples include proteins and carbohy- drates, which are compounds in living things. The smallest, simplest covalent compounds have molecules with just two atoms. An example is hydrogen chloride (HCl). It consists of one hydrogen atom and one chlorine atom, as you can see in the Figure 1.1.

instructional diagrams

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questions

in covalent compounds, elements are held together by the force of attraction between oppositely charged atoms.

a. true

-->  b. false

covalent compounds form structures called crystals.

a. true

-->  b. false

prefixes may be used in the name of a molecular compound to represent the numbers of each atom in a molecule of the compound. which prefix represents five atoms?

a) tetra-

b) tri-

-->  c) hexa-

d) penta-

which of the following is a correct rule for naming molecular compounds?

-->  a) the name of the element closer to the left side of the periodic table comes first.

b) the name of the element closer to the right side of the periodic table comes first.

c) the name of the element closer to the bottom of the periodic table comes first.

d) the name of the element closer to the top of the periodic table comes first.

which of the following is a property of most molecular compounds?

a) ability to dissolve in water

-->  b) ability to burn easily

c) ability to conduct electricity

d) very high boiling point

diagram questions

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