Good Morning! October 20, 2015October 20, 2015 Starter: Please write the formula for the following compounds (you will need your Table of polyatomic ions) Boron Sulfate Calcium Phosphate Ammonium Oxide Barium Acetate I will be coming around to check the starters too. Before we answer the starter practice problems we need to check the questions from yesterday LinkLink After that we will move on to talk about Covalent Bonding

Starter Answers Boron Sulfate B +3 SO 4 -2 Calcium Phosphate Ca +2 PO 4 -3 Ammonium Oxide NH 4 +1 O -2 Barium Acetate Ba +2 C 2 H 3 O 2 - B 2 (SO 4 ) 3 Ca 3 (PO 4 ) 2 (NH 4 ) 2 O Ba(C 2 H 3 O 2 ) 2

Good Morning 10/20/2015 Starter: Have you ever heard of Dihydrogen Monoxide? Today we will… –Working through the notes for Covalent bonding. –Passing back work –Looking at the gradesheet

Dangerous Menace Monoxide? Thousands of people die every year from inhalation of this deadly compound, and today we will discuss it.

Dihydrogen Monoxide DHMO LinkLink

The deadly molecule Dihydrogen Monoxide. The prefix Di means 2, and the prefix mono means 1. So Dihydrogen Monoxide is H 2 O –I didn’t lie to you, many people do die from too much Dihydrogen Monoxide, they drown. –True statement: this was a urban legend that went around as an that went around a few years ago and a city in Washington State banned the substance before they realized it was water!

Why the confusion? Well it turns out that Water is a Molecule that bonds covalently. That means it doesn’t transfer electrons like the compounds we studied before. Water bonds by SHARING electrons. This means that we have to have a totally different way to name these compounds.

Molecular Compounds Molecular compounds are held held together by covalent bonds, so what do you think is another name for these compounds? Covalent Compounds They share electrons for the same reason that Ionic compounds transfer electrons, They are trying to become stable.

How can you tell the difference between Ionic and Molecular? Ionic have a metal in them. The only exception that we will be working with is NH 4 + because it is a positive polyatomic and it takes the place of the metal.

The bond between two atoms that share electrons is __________. A covalent bond

Why do you need to use prefixes with molecules? They don’t have charges and there can be many different combinations.

Sharing Electrons Some atoms of nonmetals are unlikely to lose or gain electrons. Remember when we talked about the elements in Group 4? They don’t like to make ions.

Sharing Electrons They would have to either gain or lose four electrons in order to have a stable outer level. Since losing electrons takes so much energy they are willing to Share rather than try and take electrons away from each other. Video

Single Covalent Bonds A single covalent bond is made up of two shared electrons. A water molecule contains two single bonds. In each bond, a hydrogen atom contributes one electron to the bond and the oxygen atom contributes the other. The result of this type of bonding is a stable outer energy level for each atom in the molecule.

Sharing Electrons The attraction that forms between atoms when they share electrons is known as a covalent bond. The molecule is held together because the nuclei (positive because of the protons) are attracted to the electrons that are between them.

Multiple Bonds A covalent bond also can contain more than one pair of electrons. An example of this is the bond in nitrogen (N 2 ).

Multiple Bonds A nitrogen atom has five electrons in its outer energy level and needs to gain three electrons to become stable. It does this by sharing its three electrons with another nitrogen atom.

Multiple Bonds When each atom contributes three electrons to the bond, the bond contains six electrons, or three pairs of electrons. Each pair of electrons represents a bond. Therefore, three pairs of electrons represent three bonds, or a triple bond.

Naming Binary Covalent Compounds Covalent compounds are those formed between elements that are nonmetals. Some pairs of nonmetals can form more than one compound with each other. In the system you have learned so far, each of these compounds would be called nitrogen oxide. You would not know from that name what the composition of the compound is.

Using Prefixes Scientists use Greek prefixes to indicate how many atoms of each element are in a binary covalent compound. Notice that the last vowel of the prefix is dropped when the second element begins with a vowel as in pentoxide.

Rules for Naming Molecular/Covalent Compounds First word in the compound: Give the prefix designating the number of atoms of the first element present. We don’t use the prefix mono when there is only one atom of the first element. CO 2 : No prefix for C (only one) N 2 O 3 : di Name the first element. CO 2 : carbon N 2 O 3 : di nitrogen

Rules for Naming Molecular/Covalent Compounds Second word in the compound: Give the prefix designating the number of atoms of the second element present. CO 2 : carbon di N 2 O 3 : dinitrogen tri Name the root of the second element. CO 2 : carbon di ox N 2 O 3 : dinitrogen tri ox Add – ide to the root of the second element. CO 2 : carbon diox ide (official name) N 2 O 3 : dinitrogen triox ide (official name)

Rules for Writing Formulas for Molecular/Covalent Compounds First symbol in the formula: Write the symbol of the first element. Sulfur Dichloride: S Di carbon tetrabromide: C Look for a prefix for the first element if it’s there, use the table to find the right subscript. Sulfur Dichloride: S (no prefix) Di carbon tetrabromide: C 2 (di = 2)

Rules for Writing Formulas for Molecular/Covalent Compounds Second symbol in the formula: Write the symbol of the second element. Sulfur Di chlor ide: SCl Dicarbon tetra brom ide: C 2 Br Look for a prefix for the second element if it’s there, use the table to find the right subscript. Sulfur Di chloride: SCl 2 (di = 2) Dicarbon tetra bromide: C 2 Br 4 (tetra= 4)

Answers N 2 O 4 PCl 5 NO CCl 4 SCl 2 Dinitrogen Tetroxide Phosphorus Pentachloride nitrogen monoxide –or nitrogen oxide Carbon Tetrachloride Sulfur Dichloride

Answers Sulfur Hexafluoride Pentanitrogen Heptoxide Diodine tetrachloride Triastatine Octoxide Phosphorous Mononitride SF 6 N 5 O 7 I 2 Cl 4 At 3 O 8 PN