Week Four Wrap-Up
Module Review
In this module, we learned to differentiate between elements and compounds. Remembering the trends we learned in the previous module (Periodic Trends), we were able to take a closer look at the properties of elements (one type of atom; a pure substance), molecules (two atoms, chemically bonded), compounds (two or more elements, chemically bonded), and mixtures (two or more pure substances) to understand why they behave the way they do. Elements can exist as atomic (one atom), or molecular (two or more atoms of the same substance). Compounds can be molecular (two or more nonmetals), or ionic (composed of anions and cations).
There were three different types of bonding that we looked at: metallic bonding (between two or more metal atoms), ionic bonding (bonding between metal and nonmetal atoms), and covalent bonding (between two or more nonmetal atoms). Ionic bonding boils down to the transfer of electrons between atoms, specifically between a metal (electron donor) and a nonmetal (electron acceptor) atoms. We learned that covalent bonding is the sharing of electrons among atoms so that all of the atoms have enough electrons around them. Nonmetal atoms are able to do this (form different compounds using different covalent bonds) in a variety of ways. For all compounds, we learned how to write molecular formulas (chemical formulas), empirical formulas and how to represent the models of them in 3 dimensions.
We then learned about IUPAC nomenclature (the systematic rules used for naming compounds) of ionic compounds, molecular compounds, oxyacids, binary acids, and hydrates. We also learned how to divide compounds into different classes, such as organic compounds (containing primarily carbon and hydrogen), and inorganic compounds (everything else; contains subcategories used to further classify by rules and name).
After we figured out how to write the chemical formulas (and name the compounds), we learned how to calculate the molecular mass and molar mass of compounds. Molecular mass is the mass of a single unit of a compound, and is also known as the formula mass or the molecular wait and is measured in units of amu (atomic mass units). We also learned how to find the molar mass for compounds (the mass of all of the units within a compound), which is measured in grams per mole. We then used molar mass of compounds to calculate other needed values, such as mass percent of a unit within a compound. We used the mass percent of a unit of a compound to help write chemical relationships. Chemical relationships can be used to solve an unknown value (for example: the molar mass or the number of atoms of a unit) within a compound.
We then used this new information to determine the empirical formula of a compound. First, we assumed a 100 g sample, then we converted from mass to moles and then divided each moles of units within the compound by the smallest number of moles. We used this information to determine the subscripts of the units, creating the empirical formula from experimental data.
Supplemental Material
If you would like to learn more on this topic, these resources may help:
How to Speak Chemistrian: Crash Course Chemistry # 11
Completion Checklist
Make sure you complete the following learning activities and assessments before moving on to the next topic:
- Lecture Videos
- Example Videos (where posted)
- Practice Problems and Discussion
- Quiz