atoms and bonding elements and atoms atoms, bonding, and the periodic table ionic bonds covalent...
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Atoms and Bonding
Elements and Atoms
Atoms, Bonding, and the Periodic Table
Ionic Bonds
Covalent Bonds
Bonding in Metals
Table of Contents
Atoms and Bonding - Elements and Atoms
The Building Blocks of Matter
Matter may consist of elements, compounds, or mixtures.
Atoms and Bonding - Elements and Atoms
Atomic Theory and Models
Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.
Atoms and Bonding - Elements and Atoms
Atomic Theory and Models
Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.
Atoms and Bonding - Elements and Atoms
Atomic Theory and Models
Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.
Atoms and Bonding - Elements and Atoms
Atomic Theory and Models
Through the first part of the twentieth century, atomic models continued to change.
Atoms and Bonding
OutliningAs you read, make an outline about elements and atoms. Use the red headings for the main ideas and the blue headings for the supporting ideas.
Elements and Atoms
I. The Building Blocks of Matter
A. Elements, Compounds, and Mixtures
B. Particles of ElementsII. Atomic Theory and Models
A. Dalton’s Atomic TheoryB. Thomson and Smaller
Parts of AtomsC. Rutherford and the
NucleusD. Bohr’s ModelE. A Cloud of ElectronsF. The Modern Atomic
Model
- Elements and Atoms
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
The Periodic Table
Elements are organized into rows and columns based on their atomic number.
Atoms and Bonding
More on Atomic Structure
Click the PHSchool.com button for an activityabout atomic structure.
- Elements and Atoms
Atoms and Bonding
End of Section:Elements and
Atoms
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
Valence Electrons and Bonding
The 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.
Atoms and Bonding
Periodic Table Activity
Click the Active Art button to open a browser window and access Active Art about the periodic table.
- Atoms, Bonding, and the Periodic Table
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
The Periodic Table
As the number of protons (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.
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
The Periodic Table
The variety of colors in a “neon” sign results from passing an electric current through sealed glass tubes containing different noble gases.
Atoms and Bonding
Building VocabularyAfter you read the section, reread the paragraphs that contain definitions of Key Terms. Use the information you have learned to write a definition of each Key Term in your own words.
- Atoms, Bonding, and the Periodic Table
Key Terms: Examples:
valence electrons Valence electrons are electrons that are of the highest energy level and are held most loosely.
electron dot diagram The symbol for the element surrounded by dots that stand for valence electrons is an electron dot diagram.
chemical bond A chemical bond is the force of attraction that holds two atoms together as a result of the rearrangement of electrons between them.
symbol Each element is represented by a symbol, usually consisting of one or two letters.
Key Terms: Examples:
atomic number
period
groupfamily
noble gas
The atomic number of an element is the number of protons in the nucleus of an atom.
A row of elements across the periodic table is called a period.
Elements in the same column are called a group or family.
A noble gas is any element in Group 18, which consists of elements with eight valence electrons.
Key Terms: Examples:
halogen
alkali metal
A halogen is any element in Group 17, which consists of elements with seven valence electrons.
A alkali metal is any element in Group 1, which consists of elements with one valence electron.
Atoms and Bonding
End of Section:Atoms, Bonding, and the Periodic
Table
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
You 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.
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
Ions are atoms that have lost or gained electrons.
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
Ionic bonds form as a result of the attraction between positive and negative ions.
Atoms and Bonding - Ionic Bonds
Properties of Ionic Compounds
In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.
Atoms and Bonding
Previewing VisualsBefore you read, preview Figure 17. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
Formation of an Ionic Bond
Q. What is an ionic bond?
A. An ionic bond is the attraction between two oppositely charged ions.
Q. What is the overall charge on an ionic compound?
A. Overall, an ionic compound is electrically neutral.
- Ionic Bonds
Atoms and Bonding
Salt
Click the Video button to watch a movie about salt.
- Ionic Bonds
Atoms and Bonding
Links on Ionic Compounds
Click the SciLinks button for links on ionic compounds.
- Ionic Bonds
Atoms and Bonding
End of Section:Ionic Bonds
Atoms and Bonding - Covalent Bonds
How Covalent Bonds Form
The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.
Atoms and Bonding - Covalent Bonds
How Covalent Bonds Form
The oxygen atom in water and the nitrogen atom in ammonia are each surrounded by eight electrons as a result of sharing electrons with hydrogen atoms.
Atoms and Bonding - Covalent Bonds
How Covalent Bonds Form
An oxygen molecule contains one double bond, while a carbon dioxide molecule has two double bonds. A nitrogen molecule contains one triple bond.
Atoms and Bonding
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.
- Covalent Bonds
Atoms and Bonding
Comparing Molecular and Ionic Compounds
Check that the graphs are correctly set up and labeled before students plot the data.
Graphing:
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.
- Covalent Bonds
Atoms and Bonding
Comparing Molecular and Ionic Compounds
Melting points of molecular compounds are lower than those of ionic compounds.
Interpreting Data:
Describe what your graph reveals about the melting points of molecular compounds compared to those of ionic compounds.
- Covalent Bonds
Atoms and Bonding
Comparing Molecular and Ionic Compounds
Molecular compounds have weak attractive force between molecules, 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?
- Covalent Bonds
Atoms and Bonding
Comparing Molecular and Ionic Compounds
Boiling points of molecular compounds are lower than those of ionic compounds.
Interpreting Data:
How do the boiling points of the molecular and ionic compounds compare?
- Covalent Bonds
Atoms and Bonding
Comparing Molecular and 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.
- Covalent Bonds
Atoms and Bonding - Covalent Bonds
Unequal Sharing of Electrons
Fluorine 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.
Atoms and Bonding - Covalent Bonds
Unequal Sharing of Electrons
A 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.
Atoms and Bonding
Question Answer
Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions.
How do covalent bonds form? Covalent bonds form when two atoms share electrons.
What are molecular compounds?
Molecular compounds are compounds that contain molecules bonded with covalent bonds.
How does unequal sharing of electrons affect the atoms in molecular compounds?
Unequal sharing of electrons causes the bonded atoms to have slight electrical charges.
- Covalent Bonds
Atoms and Bonding
Links on Molecular Compounds
Click the SciLinks button for links on molecular compounds.
- Covalent Bonds
Atoms and Bonding
End of Section:Covalent Bonds
Atoms and Bonding - Bonding in Metals
Metallic Bonding
A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.
Atoms and Bonding - Bonding in Metals
Metallic Properties
The “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.
Atoms and Bonding
Relating Cause and EffectAs you read, identify the properties of metals that result from metallic bonding. Write the information in a graphic organizer like the one below.
Metallic bonding
Electrical conductivity
Heat conductivity
Ductility
Malleability
Luster
Cause
Effects
- Bonding in Metals
Atoms and Bonding
Links on Metallic Bonding
Click the SciLinks button for links on metallic bonding.
- Bonding in Metals
Atoms and Bonding
End of Section:Bonding in
Metals
Atoms and Bonding
Graphic Organizer
Attraction between oppositely charged ions
Feature Ionic BondPolar Covalent Bond
Nonpolar Covalent Bond
Metallic Bond
How Bond Forms
Charge on Bonded Atoms?
Example
Unequal sharing of electrons
Yes; positive or negative Yes; positive
O2 molecule
Equal sharing of electrons
Attraction between positive ions and surrounding electrons.
Yes, slightly positive or slightly negative
No
NaCl crystal (or other ionic compound)
H2O molecule (or other polar covalent molecule)
Calcium (or other metal)
Atoms and Bonding
End of Section:Graphic Organizer