Chemical Naming & Formula Writing

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What are Ionic Compounds?

• Ionic compounds consist of a cation (+ ion) and an anion (- ion)

• Monotomic cations can be found to the left of the staircase

• Monotomic anions can be found to the right of the staircase

• Ex: NaCl, CaBr2, K3PO4, NH4Cl

How are Ionic Compounds Bonded?

• Ionic compounds are formed when electrons are transferred between the cation and anion

• The cation will lose electron(s) to become stable and look like a noble gas

• The anion will gain electron(s) to become stable and look like a noble gas

How is NaCl Formed?

Na Cl

Na has 1 valence electron and Cl has 7 valence electrons.

Na will transfer its 1 valence electron to Cl so that they can both become stable and look like noble gases.

Na+1 now looks like Ne from the outer shell and Cl-1 now looks like Ar.

What Does an Ionic Formula Represent?

• An ionic formula represents the lowest whole number ratio of atoms in a compound

• This ratio is referred to an a formula unit

Na+ (green) ions will ionically bond with Cl- (purple) ions in a repeating pattern toform what is called a crystal lattice.

A formula unit is the lowest whole numberratio of the Na to Cl atoms which would be 1:1 NaCl.

Unique Properties of Ionic Compounds?

• Solids at room temperature• Relatively high melting points (>300°C) • High solubility in water• No conductivity as a solid but as an aqueous

solution or molten, they are conductive• You must have ions present in order to

conduct electric current

What are Molecular Compounds?

• Molecular compounds consist of 2 nonmetals located to the right of the staircase

• 2 types: polar and nonpolar covalent• Polar covalent compounds usually are made up

of 2 or more different nonmetals• Ex: H2O, NH3, CO• Nonpolar covalent compounds usually are made

up of 2 of the same nonmetals• Ex: Br2, Cl2, O2

How are Molecular Compounds Formed?

• For polar covalent compounds, electrons are unequally shared between the nonmetals to achieve noble gas stability

• The higher electronegative element will pull the electron(s) its sharing closer to it than the less electronegative element

• For nonpolar covalent compounds, electrons are equally shared between the nonmetals to achieve noble gas stability

Nonpolar covalent equalsharing of an electron between 2 F atoms to become more stable and look like Ne F2

H2OPolar covalent unequal sharingof an electron between eachof the 2 H atoms and the O atom allows H to look like Heand O to look like Ne. The electrons are pulled closer to because it is the moreelectronegative element

What Does a Molecular Formula Represent?

• A molecular formula represents the actual number of atoms in a compound

There are 2 H and 1 Oatoms in 1 water molecule

There are 3 H and 1 N atoms in1 ammonia molecule

Unique Properties of Polar Covalent Compounds?

• Usually liquids or gases at room temperature• Melting point is <300°C (less than ionic)• Solubility in water varies• Not conductive

Unique Properties of Nonpolar Covalent Compounds?

• Gases at room temperature (exceptions include I2 solid and Br2 liquid)

• Very low melting point (less than polar covalent)

• No solubility in water• Not conductive

What are Metallic Compounds?

• Metallic compounds consist at least one metal• Ex: Cu, Pt, Sn, Pb, Ag• Metallic compounds made up of more than 1

metal are called alloys• Ex: brass (70% Cu & 30% Zn), stainless steel,

pewter, 14K-24K Au

How are Metallic Compounds Formed?

• Metallic compounds are bonded by a sea of electrons that hold the metal cations together

The delocalized electrons do not belong to any single cation. They swim in the sea, holding the cationstogether

What Does a Metallic Compound Represent?

• Like an ionic formula, metallic formulas also represent the lowest whole number ratio of atoms in a compound

• This ratio is referred to an a formula unit

Unique Properties of Metallic Compounds?

• Solids at room temperature (exception Hg liquid)

• Very high melting points (higher than ionic)• No solubility in water• Conductive because of the mobile ions

swimming in the sea of delocalized electrons