Ionic and Covalent Compounds

Naming Molecular Compounds

1. Count the number of aroms in the first element. 2. Write the appropriate prefix followed by the name of the element. If the prefix is "mono-", omit it. 3. Count the number of atoms of the second element. 4. Write the appropriate prefix followed by the name of the element using the suffix "-ide" 5. Put it all together Ex: N₂S₃ → dinitrogen trisulfide

Writing Formulas for Polyatomic Ions

1. Use the cross-over rule. 2. Brackets are needed around the polyatomic ion if the cross-over rule indicates that more than one of them is in the formula. Ex: iron (III) nitrate → Fe(NO₃)₃

Writing Formulas for Multivalent Metals

1. Use the reverse cross-over rule if you are not given the name of the multivalent metal 2. If you are given the name of the multivalent metal, write down the charge given in the roman numeral corresponding to the metal and use the cross-over rule. Ex: Fe₂O₃ → Fe³⁺O²⁻ → Iron (III) Oxide Ex: Tin (IV) Chloride → SnCl₄

Writing Names for Multivalent Metals

1. Use the reverse cross-over rule to find charge the on multivalent metals. 2. Check that the anion has the correct charge; if not multiply both charges by the number that will correct it. 3. Put the name of metal cation, followed by charge in roman numerals, followed by the anion. Ex: CoCl₃ → cobalt (III) chloride

Writing Names for Ionic Compounds

1. Write the full name of the metal on the left. 2. Write the name of the non-metal on the right changing it so it ends with "-ide" Ex: K₂O → potassium oxide

Cross-Over Rule

1. Write the symbols for the elements with metal on the left and non-metal on right. 2. Write ionic charges 3. Select the number of ions to balance the charge; use the cross-over rule Ex: beryllium bromide: Be²⁺Br⁻ → BeBr₂

Polyatomic Ion

An ion that is made of more than one kind of atom.

Ionic Compounds

Are formed between metals and non-metals. Metals lose electrons to form cations. Non-metals gain electrons to form anions. The attracted cations and anions form the ionic compound.

Drawing a Lewis Dot Diagram for Ionic Compounds

Cations and anions combine together to form ionic compounds. Square brackets are drawn around the diagram and the charge is written in the upper rigt hand corner. The bracket on the left is always positive and empty and the one on the right is always negative and full.

Drawing a Lewis Dot Diagram

Draw a dot around the chemical symbol of the atom to represent each valaence electron of the atom. Ex: Carbon → Group 4 → 4 valence electrons

Ions

Either positively or negatively charged particles that are formed when atoms gain or lose electrons in order to get stable/filled outer shells.

Valence Electron

Electrons in the outer energy level that are responsible for the chemical properties of an atom.

Drawing a Lewis Dot Diagram for Covalent Molecules

In covalent bonds, atoms share electrons to achieve stable octets. This can be shown by drawing a line connecting the electrons/dots that are being shared. Ex: F₂

Properties of Ionic Compounds

Ionic compounds are often called salts and pure ionic compounds are always solid at room temperature. Ionic bonds are very strong resulting in very high melting and boiling points. They are soluble in water and when dissolved in water, they conduct electricity and as a result they are referred to as electrolytes. They also conduct electricity when they are molten. Their ions are arranged in a lattice structure making them rigid and brittle.

Writing Names for Polyatomic Ions

Ionic compounds that contain polyatomic ions are named the same way as binary ionic compounds. Ex: K₂CO₃ → potassium carbonate

Ionic Bonding

Is when cations and anions are held together by forces of attraction between opposite charges.

Lewis Dot Diagrams

Lewis dot diagrams show the chemical symbol of the atom and the valence electrons of the atom.

Multivalent Metals

Metals that have more than one ion charge listed in the periodic table. These metals, called multivalent metals, can form different ions depending on the chemical reaction they undergo.

Two Types of Molecules

Molecular compounds are formed when elements share electrons. Ex: H₂O Diatomic molecules are formed when two of the same atoms share electrons. There are 7 elements that always form diatomic molecules; HOFBrINCl Ex: O₂

Molecules

Molecules are formed when atoms bond covalently.

Anions

Negatively charged ions.

Cations

Positively charged ions.

Writing Formulas for Molecular Compounds

To write the formulas for molecular compounds, take the prefix of the element in the name and add it so it follows the element in the formula. DO NOT USE THE CROSS OVER RULE! Ex: diphosphorus heptoxide → P₂O₇

Covalent Bonding

When two non-metals react neither one will want to give away an electron. Instead, they share their valence electrons. This sharing of electrons is called a covalent bond.

Prefixes for Naming Molecular Compounds

mono - 1 di - 2 tri - 3 tetra - 4 penta - 5 hexa - 6 hepta - 7 octa - 8 nona - 9 deca - 10