chapter 5 atoms and bonding - chino valley unified school ... · pdf filechapter 5 atoms and...

Chapter 5 Atoms and Bonding

Table of ContentsChapter Preview

5.1 Atoms, Bonding, and the Periodic Table

5.2 Ionic Bonds

5.3 Covalent Bonds

5.4 Bonding in Metals


Chapter Preview Questions

1. The atom is made of protons, electrons, anda. valence electrons.b. neutrons.c. molecules.d. ions.



2. Reactant atoms and molecules interact to form products with

a. identical physical properties.b. different physical properties.c. identical chemical properties.d. different chemical properties.



3. In chemical reactions, the number of atomsa. varies according to the elements involved.b. changes from one reactant to another.c. stays the same.d. depends on atom arrangement.



4. Compounds are formed bya. combining two or more different elements.b. bombarding atoms with high-speed particles.c. combining two or more different nuclei.d. dissolving a solid in a liquid.


Water is a compound made fromthe elements hydrogen andoxygen. How do the propertiesof water differ from those of theelements that it is made up of?

How do compounds form?


Word Definition Example Sentence

conduct v. To allow something totravel along or through it

Metal strips on a circuit board conduct electric current.

High-Use Academic Words



stableadj. Not easily or quicklychanged from one stateto another

Gold is a stable metal thatdoes not rust or tarnish.




structuren. The way in which partsof something are puttogether.

The outside structure of thebuilding is made of brick andconcrete.




n. A written sign thatstands for something else.

The symbol for the elementoxygen is O.symbol



Apply It!

Choose the word that best completes the sentence.

1. “H” is the for hydrogen.

symbol

2. The of an atom consists of a nucleus of protons andneutrons, surrounded by a cloud of moving electrons.

structure

3. Platinum jewelry lasts a long time because the metal is very .

stable


End of Chapter Preview


Section 1:Atoms, Bonding, and

the Periodic TableHow is the reactivity of elements related to valence electrons in atoms?What does the periodic table tell you about the atoms of elements?


Valence Electrons and BondingThe number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.


How the Periodic Table WorksThe periodic table reveals the underlying atomic structure of atoms, including the arrangement of the electrons.


Periodic Table Activity

Click the Active Art button to open a browser window and access Active Art about the periodic table.


The Periodic TableAs the atomic number increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period.


End of Section:Atoms, Bonding, and

the Periodic Table


Section 2:Ionic Bonds

How do ions form bonds?How are the formulas and names of ionic compounds written?What are the properties of ionic compounds?


Ions and Ionic BondsYou and a friend walk past a market that sells apples for 40 cents each and pears for 50 cents each. You have 45 cents and want an apple. Your friend also has 45 cents but wants a pear.


Ions and Ionic BondsWhen an atom loses one of its electrons, it becomes a positively charged ion. The atom that gains the electron becomes a negatively charged ion.


Ions and Ionic BondsIons are atoms or groups of atoms that have lost or gained electrons.


Ions and Ionic BondsIonic bonds form as a result of the attraction between positive and negative ions.


Properties of Ionic CompoundsIn general, ionic compounds are hard, brittle solids with high melting points. When melted or dissolved in water, they conduct electric current.


Links on Ionic Compounds

Click the SciLinks button for links on ionic compounds.

http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=scn&wcsuffix=1213


Salt

Click the Video button to watch a movie about salt.


End of Section:Ionic Bonds


Section 3:Covalent Bonds

What holds covalently bonded atoms together?What are the properties of molecular compounds?How does unequal sharing of electrons affect molecules?


How Covalent Bonds FormThe force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.


How Covalent Bonds FormThe oxygen atom in water and the nitrogen atom in ammonia each have eight valence electrons as a result of forming covalent bonds with hydrogen atoms.


How Covalent Bonds FormDouble and triple bonds can form when atoms share more than one pair of electrons.


Comparing Molecular and Ionic Compounds

The table compares the melting points and boiling points of a few molecular compounds and ionic compounds. Use the table to answer the following questions.


Comparing Molecular and Ionic CompoundsGraphing:

Create a bar graph of just the melting points of these compounds. Arrange the bars in order of increasing melting point. The y-axis should start at –200ºC and go to 900ºC.

Check that the graphs are correctly set up and labeled before students plot the data.


Comparing Molecular and Ionic CompoundsInterpreting Data:

Describe what your graph reveals about the melting points of molecular compounds compared to those of ionic compounds.

Melting points of molecular compounds are lower than those of ionic compounds.



Molecular compounds have weak attractive force between molecules compared to those between ions, so less energy is needed to melt molecular compounds.

Inferring:

How can you account for the differences in melting points between molecular compounds and ionic compounds?


Comparing Molecular and Ionic CompoundsInterpreting Data:

How do the boiling points of the molecular and ionic compounds compare?

Boiling points of molecular compounds are lower than those of ionic compounds.



Students may predict that ammonia is a molecular compound because it has relatively low melting and boiling points.

Predicting:

Ammonia’s melting point is –78ºC and its boiling point is –34ºC. Is ammonia a molecular compound or an ionic compound? Explain.


Unequal Sharing of ElectronsFluorine forms a nonpolar bond with another fluorine atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.


Unequal Sharing of ElectronsA carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.


Links on Molecular Compounds

Click the SciLinks button for links on molecular compounds.



End of Section:Covalent Bonds


Section 4:Bonding in Metals

How do the properties of metals and alloys compare?How do metal atoms combine?How does metallic bonding result in useful properties of metals?


Metallic BondingMetal atoms combine in regular patterns in which the valence electrons are free to move from atom to atom.


Metallic PropertiesThe “sea of electrons”model of solid metals explains their ability to conduct heat and electricity, the ease with which they can be made to change shape, and their luster.


Links on Metallic Bonding

Click the SciLinks button for links on metallic bonding.



End of Section:Bonding in Metals


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