Outcome: Students will classify elements in the periodic table and model the formation of ionic bonds. Warm-up: 1. Why do atoms form bonds? 2. How are ions formed? 3. Write the symbol and charge of the following ions. Potassium loses one electron Sulfur gains two electrons Iron loses three electrons Nitrogen gains three electrons
Where does table salt come from? In some countries, salt is obtained by the evaporation of seawater. In other countries, salt is mined from rock deposits deep underground. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Formation of Ionic Compounds What is the electrical charge of an ionic compound? Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Review Ionic Bond K + Br K + + Br -
Formation of Ionic Compounds Sodium chloride, or table salt, is an ionic compound consisting of sodium cations and chloride anions. An ionic compound is a compound composed of cations and anions. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Although they are composed of ions, ionic compounds are electrically neutral. The total positive charge of the cations equals the total negative charge of the anions. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Ionic Bonds Anions and cations have opposite charges and attract one another by means of electrostatic forces. The electrostatic forces that hold ions together in ionic compounds are called ionic bonds. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Ionic Bonds When sodium and chlorine react to form a compound, the sodium atom transfers its one valence electron to the chlorine atom. Sodium and chlorine atoms combine in a one-toone ratio, and both ions have stable octets. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Ionic Bonds Aluminum metal (Al) and the nonmetal bromine (Br 2 ) react violently to form the ionic solid aluminum bromide (AlBr 3 ). Each bromine atom has seven valence electrons and readily gains one additional electron. Three bromine atoms combine with each aluminum atom. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Formula Units A chemical formula shows the numbers of atoms of each element in the smallest representative unit of a substance. NaCl is the chemical formula for sodium chloride. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Formula Units Ionic compounds do not exist as discrete units, but as collections of positively and negatively charged ions arranged in repeating patterns. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Formula Units The chemical formula of an ionic compound refers to a ratio known as a formula unit. A formula unit is the lowest wholenumber ratio of ions in an ionic compound. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Formation of Ionic Compounds Formula Units For sodium chloride, the lowest wholenumber ratio of the ions is 1:1 (one Na + ion to each Cl ion). The formula unit for sodium chloride is NaCl. Although ionic charges are used to derive the correct formula, they are not shown when you write the formula unit of the compound. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 Predicting Formulas of Ionic Compounds Use electron dot structures to predict the formulas of the ionic compounds formed from the following elements: a. potassium and oxygen b. magnesium and nitrogen Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 1 Analyze Identify the relevant concepts. Atoms of metals lose valence electrons when forming an ionic compound. Atoms of nonmetals gain electrons. Enough atoms of each element must be used in the formula so that electrons lost equal electrons gained. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. a. Start with the atoms. K and O Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. a. In order to have a completely filled valence shell, the oxygen atom must gain two electrons. These electrons come from two potassium atoms, each of which loses one electron. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. a. Express the electron dot structure as a formula. The formula of the compound formed is K 2 O (potassium oxide). Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. b. Start with the atoms. Mg and N Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. b. Each nitrogen atom needs three electrons to have an octet, but each magnesium atom can lose only two electrons. Three magnesium atoms are needed for every two nitrogen atoms. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample Problem 7.1 2 Solve Apply the concepts to this problem. b. Express the electron dot structure as a formula. The formula of the compound formed is Mg 3 N 2 (magnesium nitride). Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Properties of Ionic Compounds Properties of Ionic Compounds What are three properties of ionic compounds? Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Properties of Ionic Compounds Most ionic compounds are crystalline solids at room temperature. The component ions in such crystals are arranged in repeating threedimensional patterns. The beauty of crystalline solids comes from the orderly arrangement of their component ions. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Properties of Ionic Compounds Each ion is attracted strongly to each of its neighbors, and repulsions are minimized. The large attractive forces result in a very stable structure. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Properties of Ionic Compounds Ionic compounds generally have high melting points. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
CHEMISTRY & YOU Would you expect to find sodium chloride in underground rock deposits as a solid, liquid, or gas? Explain. Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
CHEMISTRY & YOU Would you expect to find sodium chloride in underground rock deposits as a solid, liquid, or gas? Explain. Sodium chloride is found in underground rock deposits as a solid. Like most ionic compounds, sodium chloride has a high melting point (about 800 C). Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved.
Review Ionic Bond Ca + Cl 2+ - Ca + 2 Cl Cl
Warm-up: Use your periodic table to answer the following questions: 1. List 3 examples of alkali metals. 2. List 2 examples of alkaline-earth metals. 3. List 2 liquid elements at room temperature. 4. List 2 examples of halogens. 5. Name an example of inner transition metal. 6. List 3 examples of transition metals. 7. List 5 examples of metalloids. 8. List 2 examples of noble gases.
Two types of compounds Ionic- occurs when a metal loses electrons to a nonmetal. The metal becomes a cation and the nonmetal becomes anion. Covalent- two nonmetals share electrons. Neither lose or gain electrons they share electrons. Neither atoms become ions.
Ionic Compounds
How to write an ionic formula? 1. Write the symbols of the two elements. 2. Write the charge of each as superscripts. 3. Drop the positive and the negative signs. 4. Crisscross the superscripts so that they become subscripts. 5. Reduce when possible.
Formula for aluminum oxide 1. Write the symbols of the elements. Al O
Formula for Aluminum oxide 2. Write the charges as superscripts. Al +3-2 O
Formula for Aluminum oxide 3. Drop the + and - signs. + 3-2 O Al
Formula for Aluminum oxide 4. Crisscross the charges so that they become subscripts. Al 3 2 O
Formula for Aluminum oxide 4. Crisscross the charges so that they become subscripts. Al O 3 2
Reduce the subscript when possible Mg 2 O 2
Naming Ionic Compounds
Naming Ionic Compounds 1. Name the metal first followed by the nonmetal with an ide ending. 2. For transition metals, roman numeral is used to indicated the valence electron (charge).
Most transition metals have more than 1 valence electron Roman Numeral is used to indicated VE. Examples. Iron (II) Fe +2 Copper (I) Cu +
Polyatomic Ions NH + 4 ammonium OH hydroxide NO - 3 nitrate NO 2 nitrite SO -2 3 sulfite SO -2 4 sulfate CO -2 3 carbonate PO -3 4 phosphate Oxyanions
Ternary Compounds Compounds with 3 elements in them Cation Anion Formula Ca +2 NO - 3 Ca(NO 3 ) 2 Mg +2 PO -3 4 Mg 3 (PO 4 ) 2 Ba +2 OH - Ba(OH) 2 Ba +2 SO -2 4 BaSO 4
CO(sharing)VALENT Bonds Sharing of electrons Covalent compounds
Matter Elements Compounds
How? 1. Total valence electrons of the atoms involved 2. Central Atom 3. Bond the terminal atoms to the central atom. (Remember: 1 bond= a pair of e-) 4. Distribute the remaining e- to the terminal atoms first (in pairs), then to the central atom. 5. Check if each atom is stable (should have 8e- / H is stable at 2e-.
Practice Draw the Lewis Structure of the following compounds. 1. H 2 O 2. CCl 4 3. NH 3
H 2 O Total valence e-: 1 (2) + 6 = 8 Central atom: O H O H Distribute 8 e- to the terminal atoms first, then central atom last
Polar
Non polar