Chemical Bonds Chapter 19 IPC

Combined Elements Some elements combine chemically and no longer have the same properties they did before forming a compound. Some elements combine chemically and no longer have the same properties they did before forming a compound. Example: NaCl Example: NaCl + = + = + Sodium Chlorine Table Salt

Formulas Chemical formula – composed of symbols and subscripts indicating the number of atoms of an element in a compound. Chemical formula – composed of symbols and subscripts indicating the number of atoms of an element in a compound. Example: NH 3 Example: NH 3 1 Nitrogen atom 1 Nitrogen atom 3 Hydrogen atoms 3 Hydrogen atoms

Atomic Stability Atoms form compounds when the compound is more stable than separate atoms. Atoms form compounds when the compound is more stable than separate atoms. Noble gases are more chemically stable than other elements because they have a complete outer energy level. Noble gases are more chemically stable than other elements because they have a complete outer energy level. Elements that do not have full outer energy levels are more stable in compounds. Elements that do not have full outer energy levels are more stable in compounds.

Atomic Stability Atoms can lose, gain, or share electrons to get a stable outer energy level. Atoms can lose, gain, or share electrons to get a stable outer energy level. A chemical bond is the force that holds atoms together in a compound. A chemical bond is the force that holds atoms together in a compound.

Question 1 Why do elements form compounds? Why do elements form compounds? A. To become radioactive B. To become unstable C. To become more chemically stable D. To maintain the same properties

Question 2 How many hydrogen atoms are in the compound NaHCO 3 ? How many hydrogen atoms are in the compound NaHCO 3 ? A. 0 B. 1 C. 2 D. 3

Gain or Loss of Electrons An atom that has gained or lost an electron is an ion. An atom that has gained or lost an electron is an ion. A superscript indicates the charge. A superscript indicates the charge. Examples: Examples: Potassium Bromide and Sodium Chloride Potassium Bromide and Sodium Chloride

The Ionic Bond Ionic bond - the force of attraction between opposite charges of the ions. Ionic bond - the force of attraction between opposite charges of the ions. Formed between metals and nonmetals. Formed between metals and nonmetals. The result of the bond is a neutral compound. The result of the bond is a neutral compound. The sum of the charges on the ions is zero. The sum of the charges on the ions is zero.

Ionic Bonding Sodium loses an electron and Chlorine gains an electron in ionic bonding. Sodium loses an electron and Chlorine gains an electron in ionic bonding.

Molecules Neutral particles formed as a result of sharing electrons. Neutral particles formed as a result of sharing electrons. Group 4 commonly shares electrons, because it requires too much energy to lose or gain 4 electrons. Group 4 commonly shares electrons, because it requires too much energy to lose or gain 4 electrons.

The Covalent Bond Covalent bond - the force of attraction between atoms sharing electrons. Covalent bond - the force of attraction between atoms sharing electrons. Atoms can form double or triple bonds depending on whether they share two or three pairs of electrons. Atoms can form double or triple bonds depending on whether they share two or three pairs of electrons.

Polar vs. Nonpolar A polar molecule has one end that is slightly negative and one end that is slightly positive. A polar molecule has one end that is slightly negative and one end that is slightly positive. In a nonpolar molecule electrons are shared equally. In a nonpolar molecule electrons are shared equally.

Question 3 What type of bond would form between Magnesium and chlorine? What type of bond would form between Magnesium and chlorine? A. Metallic B. Ionic C. Covalent

Question 4 When an atoms loses an electron it becomes When an atoms loses an electron it becomes A. A positively charged ion B. A negatively charged ion C. A neutral atom

Question 5 The charge of a compound is The charge of a compound is A. Negative B. Positive C. Neutral

Binary Compounds Binary compound – composed of two elements Binary compound – composed of two elements Oxidation Number – how many electrons an atom has gained, lost, or shared to become stable. Oxidation Number – how many electrons an atom has gained, lost, or shared to become stable. Use the name of the first element, the root name of the second element, and the suffix – ide to write the name of a binary ionic compound. Use the name of the first element, the root name of the second element, and the suffix – ide to write the name of a binary ionic compound. Example: Calcium + Fluorine = Calcium fluoride. Example: Calcium + Fluorine = Calcium fluoride.

Writing Formulas 1. Write the symbol of the element that has a positive oxidation number. 2. Write the symbol of the element with the negative oxidation number. 3. Use subscripts next to each ion so that the sum of all the ions is zero.

Polyatomic Ion Polyatomic ion – positively or negatively charged, covalently bonded group of atoms. Polyatomic ion – positively or negatively charged, covalently bonded group of atoms. contains 3 or more elements contains 3 or more elements Write the name of the positive ion first, then the name of the negative ion. Write the name of the positive ion first, then the name of the negative ion. Example: OH = hydroxide Example: OH = hydroxide

Polyatomic Ions ChargeNameFormula 1+ammonium NH 4 1-acetate C2H3O2C2H3O2C2H3O2C2H3O2 1-chlorate ClO 3 1-hydroxideOH 1-nitrate NO 3 2-carbonate CO 3 2-sulfate SO 4 3-phosphate PO 4

Question 6 What is a binary compound? What is a binary compound? A. A compound with three or more elements. B. One that is formed from two elements. C. A compound with water chemically attached to its ions.

Question 7 Which is a binary ionic compound? Which is a binary ionic compound? A. O 2 B. NaF C. H 2 SO 4

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