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Ions and Ionic Compounds

Ions and Ionic Compounds. Indrocution to Bonding. Ionic and Covalent bonding (7 minutes). Simple Ions. Some elements are highly reactive while others are not Remember that elements want to be stable by having 8 valence electrons This is called the octet rule.

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Ions and Ionic Compounds

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  1. Ions and IonicCompounds

  2. Indrocution to Bonding • Ionic and Covalent bonding (7 minutes)

  3. Simple Ions • Some elements are highly reactive while others are not • Remember that elements want to be stable by having 8 valence electrons • This is called the octet rule

  4. Elements without the ns2 np6 configuration will react to gain or lose electrons to satisfy the octet rule • We can see this easily as potassium is added to water. An explosion occurs due to the readiness of potassium to give up an electron. • reaction

  5. Valence Electrons • The number of electrons in the outermost energy level is the number of valence electrons. • Remember how we used the periodic table to determine electron configurations and the number of valence electrons.

  6. Ions • All atoms are neutral because they have an equal number of protons and electrons. • If an atom loses one electron to become more stable, a change occurs in the atom.

  7. Ions • Potassium has 19 protons and 19 electrons and is neutral. • If the Potassium atom gives up 1 electron to be more stable it now has 19 protons and 18 electrons • Now there is a net electrical charge of +1

  8. Ions • An atom that has a net electrical charge is called an ion. • This happens when an atom or molecule has lost or gained electrons, resulting in a negative or positive charge.

  9. Ions • An ion with a positive charge is called a cation. K+ , Ca+2 • Notice the + in the name! • An ion with a negative charge is called an anion. Cl- , O-2

  10. Most metals form cations because less energy is needed to remove a few electrons than to gain several • Most nonmetals form anions for the opposite reason • Exceptions can occur on step

  11. Ionic Bonding and Salts • Since opposite charges attract, cations and anions are attracted to each other • The attraction of cations and anions form an ionic bond • Ex: Na + Cl → NaCl

  12. Ionic Bonding • Sodium gives up an electron to form a stable sodium cation while chlorine receives an electron to form a stable chlorine anion • An ionic bond has been formed

  13. Salts • A salt is often the generic name used for ionic compounds • Salts are neutral • Formation of salts is an exothermic process

  14. Ionic Compounds • Ionic compounds have distinctive properties • High melting points • High boiling points • Hard and brittle • Solid at room temperature • Good conductors in liquid phase

  15. “Perhaps one of you gentlemen would mind telling me just what is outside the window that you find so attractive..?” Image courtesy NearingZero.net

  16. How do ions combine to make compounds? • The charge of ionic compounds is always neutral. • Ionic compound: a compound composed of positive and negative ions that are combined so the numbers of positive and negative charges are equal. • We use a thing called the criss-cross rule to determine the ratio of these substances.

  17. Step 4: AlCl 3 Criss-Cross Rule Example: Aluminum & Chlorine Aluminum Chlorine Step 1: Determine which is metal and Which is non-metal Al Cl 3+ 1- Step 2: write symbols & charge of elements Al Cl Step 3: 1 3 criss-cross charges as subsrcipts combine as formula unit Reduce if necessary (“1” is never shown)

  18. Criss-Cross Rule Example: Aluminum Chloride Step 1: Aluminum Chloride Step 2: Al3+ Cl1- Step 3: Al Cl 1 3 Step 4: AlCl 3

  19. Criss-Cross Rule Example: Aluminum & Oxygen Step 1: Aluminum Oxygen Step 2: Al3+ O2- Step 3: Al O 2 3 Step 4: Al2O3

  20. Criss-Cross Rule Example: Magnesium & Oygen Step 1: Magnesium Oxygen Step 2: Mg2+ O2- Step 3: Mg O 2 2 Step 4: Mg2O2 Step 5: MgO

  21. Naming Ionic Compounds • Naming ionic compounds, or salts, is very easy if made up of a simple cation and simple anion

  22. Practice: • Examples from chart. • Complete chart

  23. Naming Ionic Compounds • These kinds of salts are known as binary ionic compounds • Binary means compound is made up of only two elements • Simple cations borrow their names from the elements • Examples: • K+ potassium • Zn+2 zinc

  24. Naming Ionic Compounds • The name of the simple anion is formed from the element name but with the ending –ide • Ex: Cl- Chloride P-3 Phosphide Br- Bromide

  25. To name Ionic Binary Comounds you simply name the cation followed by the anion. • Examples: • ZnS • K2O • Mg3N2 • Al2S3

  26. Practice: • Write the formulas for the binary ionic compounds formed between the following elements • Potassium and Iodine • Magnesium and Chlorine • Sodium and Sulfur • Aluminum and Sulfur • Aluminum and nitrogen

  27. Transition Metals • Some elements, such as iron, form two or more cations with different charges. • To distinguish the ions formed by these elements, the Stock system of nomenclature is used. • Roman numerals are used to indicate the charge of the ion. • The roman numeral is enclosed in parentheses and placed immediately after the metal name. • Examples: • Silver(I) nitrate • Iron (II) sulfate

  28. Transition Metals with Charges

  29. Examples • Name the following compounds: • CuCl2 • VBr3 • Write the formulas of the following compounds: • Iron(III) sulfide • Vanadium (II) fluoride

  30. Practice: • Name the compound or write the formula for each compound: • CuO • CoF3 • SnI4 • K2O • Copper(II) bromide • Mercury (II) sulfide • Lead (IV) sulfide

  31. Polyatomic Ions • So far we have discussed compounds with just two ions which were called binary ionic compounds since made up of just two elements • Ions can be made of a single atom or groups of atoms that make up one ion

  32. Polyatomic Ions • The term polyatomic ion means two or more bonded atoms with a charge can be considered a single ion • The charge of a polyatomic ion is distributed among the group of atoms which are bonded together • Ex: NH4+ , CrO4-2

  33. Polyatomic Ions • We name compounds containing polyatomic ions as we do binary ionic compounds with one exception. • Like binary ionic compounds, the name of the cation is named first. The name of the anion then follows. We do not change the ending to –ide! • Ex: Silver Nitrate and Silver Nitrite • Ex: NaOH and FeClO2

  34. Practice • Give the formula or name of the compound, whichever is appropriate: • Copper(II) sulfate • Ca(OH)2 • KClO3 • Lithium nitrate • Ag2O • Sodium carbonate • Fe2(CrO4)3 • Potassium perchlorate

  35. Naming Covalent Compounds • Naming covalent compounds made up of two elements are named by similar method as ionic compounds • The first element named is usually the first one written in the formula. • The second element has the ending “–ide.”

  36. Because covalent compounds are often made of the same elements, we must distinguish between two molecules made of the same elements. • For example, NO and NO2 cannot have the same name!

  37. We use a system of prefixes to show the number of atoms of each element in the molecule . • The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel • For instance, we would write monoxide and pentoxide instead of mono-oxide and penta-oxide.

  38. Prefixes for Covalent compounds

  39. Practice: • Name the following or write the formula • PF5 • XeF4 • CCl4 • Carbon dioxide • Dinitrogenpentoxide • Sulfur hexafluoride

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