The Building Blocks of Matter - Elements and Atoms The Building Blocks of Matter Matter may consist of elements, compounds, or mixtures.

Atomic Theory and Models - Elements and Atoms Atomic Theory and Models Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.

Atomic Theory and Models - Elements and Atoms Atomic Theory and Models Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.

Atomic Theory and Models - 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.

Atomic Theory and Models - Elements and Atoms Atomic Theory and Models Through the first part of the twentieth century, atomic models continued to change.

Valence Electrons 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.

The Periodic Table - Atoms, Bonding, and the Periodic Table Elements are organized into rows and columns based on their atomic number.

The Periodic Table - Atoms, Bonding, and 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.

The Periodic Table - Atoms, Bonding, and 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.

Building Vocabulary - Atoms, Bonding, and the Periodic Table After 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. Key Terms: Examples: atomic number period group family noble gas Key Terms: Key Terms: Examples: halogen alkali metal Examples: valence electrons Valence electrons are electrons that are of the highest energy level and are held most loosely. A halogen is any element in Group 17, which consists of elements with seven valence electrons. The atomic number of an element is the number of protons in the nucleus of an atom. electron dot diagram The symbol for the element surrounded by dots that stand for valence electrons is an electron dot diagram. A alkali metal is any element in Group 1, which consists of elements with one valence electron. A row of elements across the periodic table is called a period. 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. 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. symbol Each element is represented by a symbol, usually consisting of one or two letters.

Ions and Ionic Bonds - 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.

Ions and Ionic Bonds - 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.

Ions and Ionic Bonds - Ionic Bonds Ions are atoms that have lost or gained electrons.

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

Properties of Ionic Compounds - 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.

Formation of an Ionic Bond - Ionic Bonds Previewing Visuals Before 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.

Click the Video button to watch a movie about salt. - Ionic Bonds Salt Click the Video button to watch a movie about salt.

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.

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.

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.

Comparing Molecular and Ionic Compounds - Covalent Bonds 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 Compounds - Covalent Bonds Comparing Molecular and Ionic Compounds 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. Check that the graphs are correctly set up and labeled before students plot the data.

Comparing Molecular and Ionic Compounds - Covalent Bonds Comparing Molecular and Ionic Compounds Interpreting 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.

Comparing Molecular and Ionic Compounds - Covalent Bonds Comparing Molecular and Ionic Compounds Inferring: How can you account for the differences in melting points between molecular compounds and ionic compounds? Molecular compounds have weak attractive force between molecules, so less energy is needed to melt molecular compounds.

Comparing Molecular and Ionic Compounds - Covalent Bonds Comparing Molecular and Ionic Compounds Interpreting 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.

Unequal Sharing of Electrons - 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.

Unequal Sharing of Electrons - 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.

Asking Questions - Covalent Bonds Before 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. Question Answer 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.

Metallic Bonding - Bonding in Metals A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.

Metallic Properties - Bonding in Metals 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.

Relating Cause and Effect - Bonding in Metals Relating Cause and Effect As you read, identify the properties of metals that result from metallic bonding. Write the information in a graphic organizer like the one below. Effects Electrical conductivity Heat conductivity Cause Metallic bonding Ductility Malleability Luster

Graphic Organizer Polar Covalent Bond Nonpolar Covalent Bond Metallic Bond Feature Ionic Bond Attraction between oppositely charged ions Attraction between positive ions and surrounding electrons. How Bond Forms Unequal sharing of electrons Equal sharing of electrons Charge on Bonded Atoms? Yes, slightly positive or slightly negative Yes; positive or negative No Yes; positive H2O molecule (or other polar covalent molecule) NaCl crystal (or other ionic compound) Example Calcium (or other metal) O2 molecule