Section IV: Moving Electrons Lesson 17 Technicolor Atoms Lesson 18 Life on the Edge Lesson 19 Noble Gas Envy

Day 28 Lesson 17: Technicolor Atoms Flame Tests

ChemCatalyst These drawings are models that show solid copper, solid copper chloride, and aqueous copper chloride as collections of atoms. 1. Describe each model. 2. What is similar about each model? What is different? Cu(s) Solid copper CuCl2(s) Solid copper (II) chloride CuCl2(aq) Aqueous copper (II) chloride

Key Question What evidence is there that certain atoms are present in a compound?

You will be able to: conduct a flame test and use the results to determine the identity of a compound interpret evidence of the presence of certain atoms within compounds

Prepare for the Lab Work in groups. You will be using chemicals and fire today. Follow safety instructions. Wear safety goggles. Tie back long hair and remove dangling jewelry. Roll up long sleeves and keep clothing away from flames. Locate the eye wash, fire blanket, and fire extinguisher before starting the lab.

Discussion Notes The metal element in each chemical formula appears to be responsible for the flame colors. Only certain elements produce colorful flames. Flame test: A test used in the laboratory to look for the presence of certain metal atoms. A sample of a compound is heated in a flame, and the resulting color is noted.

Discussion Notes (cont.) Elements and compounds are collections of atoms. The only way to change one atom into another is to change the nucleus through a nuclear reaction.

Discussion Notes (cont.) Sodium Atom, Na

Discussion Notes (cont.) The illustration indicates that the flame colors are associated with movements of the electrons within the sodium atom. Bohr’s model of the atom came directly from evidence similar to that produced in class today.

Wrap Up What evidence is there that certain atoms are present in a compound? Many metal atoms produce a characteristic colored flame when compounds containing those atoms are heated in a flame. Flame tests are evidence that elements and compounds are collections of atoms.

Check-in Predict the flame colors produced when heating these substances. Explain your thinking. • copper (II) carbonate • calcium chloride

Day 29 Lesson 18: Life on the Edge Valence and Core Electrons

ChemCatalyst What do you notice about the number of spokes on the circles? The spokes represent electrons. Do the spokes represent the total number of electrons? Explain your thinking.

Key Question Why do elements in the same group in the periodic table have similar properties?

You will be able to: create a shell model diagram of an atom, placing the correct number of electrons in the correct shells explain the difference between a valence electron and a core electron describe the patterns in the periodic table associated with electron arrangements

Prepare for the Activity Work in pairs.

Prepare for the Activity (cont.) The Shell Model The surface of each sphere represents an area where an electron or a group of electrons is most likely to be found.

Prepare for the Activity (cont.) Electron shells are the levels around the nucleus where electrons can be found. Sodium and magnesium have electrons in three electron shells.

Discussion Notes The atomic number of an element is the same as the total number of electrons. The period (row) number of the element is the same as the number of electron shells. For main-group elements, the group number of the element is the same as the number of electrons in the outermost shell.

Discussion Notes (cont.) Table of Valence and Core Electrons

Discussion Notes (cont.) Valence shell: The outermost electron shell in an atom. Valence electrons: The electrons located in the outermost electron shell of an atom. Core electrons: All other electrons in an atom besides the valence electrons.

Discussion Notes (cont.) The arrangement of electrons in their shells is highly predictable. The numbers of core electrons also exhibit patterns across each row of the periodic table.

Wrap Up Why do elements in the same group in the periodic table have similar properties? Electrons occupy distinct areas around the nucleus called electron shells. The arrangement of electrons in these shells is highly predictable. For main group elements, elements in the same group have the same number of valence electrons. The number of valence electrons increases across a period. The number of shells and the number of core electrons increase as you go down a group.

Day 30 ChemCatalyst Provide each piece of information for element 34. a. The element’s name and symbol. b. The total number of electrons in an atom of this element. c. The number of core electrons in an atom of this element. d. The number of valence electrons. e. The group number for this element. f. The names of other elements with the same number of valence electrons.

Lesson 19: Noble Gas Envy Ions

Day 31 - ChemCatalyst Chemists have found that metal atoms transfer electrons to nonmetal atoms when they form compounds. Examine the shell model showing how a lithium atom might transfer an electron to a fluorine atom. What effect does this electron transfer have on the charge of each atom? What element does each atom resemble after the electron has been transferred?

Key Question How is chemical stability related to the arrangements of electrons in atoms?

You will be able to: explain that an ion is formed when an atom loses or gains electrons and state the difference between a cation and an anion determine the charge on an ion based on an atom’s placement in the periodic table explain the relationship between ion charge and valence electrons

Prepare for the Activity Work in groups of eight. Ion: An atom (or group of atoms) that has a positive or negative charge because it has lost or gained electrons.

Discussion Notes The table of arranged ion cards shows that the charges on ions are quite predictable.

Discussion Notes (cont.) When electrons are removed from or added to an atom, the rest of the atom stays the same. The charge on an ion is noted with a superscript.

Discussion Notes (cont.) Cation: An ion with a net positive charge. Usually these are formed from metal atoms. Anion: An ion with a net negative charge. Usually these are formed from nonmetal atoms.

Discussion Notes (cont.) Electron arrangements of atoms in ionic compounds resemble noble gases.

Discussion Notes (cont.) Atoms tend to lose or gain electrons to attain the electron arrangement of a noble gas.

Wrap Up How is chemical stability related to the arrangements of electrons in atoms? When atoms gain or lose electrons, they form ions. Ions are atoms that carry a net positive or net negative charge. When atoms lose electrons, they have a positive charge and are called cations. When atoms gain electrons, they have a negative charge and are called anions. Ions have electron arrangements resembling those of the noble gas atoms.

Day 32 ChemCatalyst Draw a shell model for calcium, Ca, showing the arrangement of its electrons. What would have to happen for an atom of calcium to have an electron arrangement like that of a noble gas? Explain.