Presentation is loading. Please wait.

Presentation is loading. Please wait.

Section 7.1 Ion formation Chapter 7 Ionic Compounds and Metals.

Similar presentations

Presentation on theme: "Section 7.1 Ion formation Chapter 7 Ionic Compounds and Metals."— Presentation transcript:

1 Section 7.1 Ion formation Chapter 7 Ionic Compounds and Metals

2 Chemical Bonds A chemical bond is the force that holds two atoms together. Can form by the attraction between the positive nucleus of one atom and the negative electrons of another Can form between positive and negative ions

3 Valence Electrons Electrons in the outermost principal energy level Shown in the electron dot structures Octet rule – atoms will gain, lose or share electrons to obtain 8 valence electrons The valence electrons determine the bonding properties of the atom

4 Positive Ion Formation A positively charged ion is called a cation. Positive ions are formed when an atom loses one or more valence electrons Metals make positive ions

5 Negative Ion Formation A negatively charged ion is called an anion. Negative ions are formed when an atom gains one or more electrons in its valence shell. Nonmetals make negative ions.

6 7.2: Ionic bonds and ionic compounds Formation of an Ionic Bond An ionic bond is the electrostatic force that holds oppositely charged particles together in an ionic compound Compounds that contain ionic bonds are called ionic compounds. Ionic compounds are formed between metals (+ charge) and nonmetals (- charge).

7 Binary Ionic Compounds Contain a metallic cation and a nonmetallic anion. Formation of Binary Ionic Compounds – Electron(s) is/are transferred from metal to nonmetal – Metal becomes positive, nonmetal becomes negative – Opposite charges attract

8 Properties of Ionic Compounds Take the structure of a crystal lattice – Many units of positive and negative ions stick together in a three-dimensional geometric arrangement Can conduct electricity when dissolved in water (they are electrolytes and break into ions when dissolved in water), but not in solid form Melting point, boiling point and hardness depend upon how strongly the ions are attracted to each other

9 Formulas for Ionic Compounds Monatomic ions are one-atom ions – Examples: Mg 2+, Br -1 Oxidation numbers are the charges on ions – Note: some elements have multiple oxidation states – you will have a periodic table to tell this Binary ionic compounds are made of two monatomic ions (one positive, one negative)

10 Formulas for Binary Ionic Compounds Symbol for cation is written first, anion second Subscripts tell the number of atoms of each element What are the following compounds made of? – CaF 2 1 calcium, 2 fluorine – Na 2 S 2 sodium, 1 sulfur – NaCl 1 sodium, 1 chlorine

11 Naming Binary Ionic Compounds Name the cation first Name the anion second with –ide at the end Examples – CaF 2  calcium fluoride – Na 2 S  sodium sulfide – NaCl  sodium chloride

12 Try Naming a few more Binary Ionic Compounds K 2 Opotassium oxide Al 2 S 3 aluminum sulfide Na 3 Nsodium nitride

13 What if the cation has more than one oxidation state? You tell which ion was used by putting a Roman Numeral after the name of the cation Example: – CuS We know S was -2 (that’s the only one it makes) If there is only one atom of each element, the Cu must have been +2 So, the name is written as Copper (II) sulfide [the “II” indicates the charge] Make sure, especially with transition elements, that you are checking the oxidation states

14 Writing Formulas for Binary Ionic Compounds Look up the charges for each element For a compound to form, the total charge must balance out to zero (positive charges must equal negative charges) Example: – Sodium bromide Na is +1, Br is -1 Only need one of each to balance Formula is NaBr

15 Try writing some more formulas Binary Ionic Compounds Potassium IodideKI Aluminum bromideAlBr 3 Magnesium chlorideMgCl 2 Cesium nitrideCs 3 N

16 Formulas for Polyatomic Ionic Compounds Polyatomic ions are ions that are made up of more than one atom You will have a chart for these and do not have to memorize them. Examples: – SO 4 2- = sulfate – CN - = cyanide – NH 4 + = ammonium

17 Naming Polyatomic Ionic Compounds Name the cation first, anion second Name the polyatomic as is – don’t change its name at all Examples: – Ca 3 (PO 4 ) 2 calcium phosphate – Mg(CN) 2 magnesium cyanide – NH 4 Clammonium chloride

18 Now you try naming Polyatomic Ionic Compounds NaNO 3 sodium nitrate Ca(ClO 3 ) 2 calcium chlorate Al 2 (CO 3 ) 3 aluminum carbonate

19 Writing formulas for Polyatomic Ionic Compounds Same as binary ionic compounds EXCEPT you may not change anything in the polyatomic ion formula Put them in a (parenthesis) and put subscripts outside that parenthesis Example: – Calcium Nitrate Ions are Ca 2+ and NO 3 - Formula will be Ca(NO 3 ) 2

20 Now you try writing formulas for Polyatomic Ionic Compounds Sodium hydroxideNaOH Copper (II) nitrateCu(NO 3 ) 2 Silver chromateAg 2 CrO 4

21 7.3: Metallic bonds and the properties of metals The electron sea model proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons Since the electrons are free to move, they are called delocalized electrons A metallic bond is the attraction of a metallic cation for delocalized electrons

22 Properties of Metals (revisited) Moderately high melting points High boiling points Malleable, ductile, durable Conduct heat and electricity well Transition metals are harder/stronger than alkali metals because the transition metals have more delocalized electrons

Download ppt "Section 7.1 Ion formation Chapter 7 Ionic Compounds and Metals."

Similar presentations

Ads by Google