Chemistry
Chapter 2:3-6
Homework
The Periodic Table
Chapter 2: 3-6 Homework
- Reading Preparation
- WebLecture
- Study Activity
- Preparation work for chat
- Online Quiz
- Lab Instructions
Reading Preparation
Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 2: Sections 3-6.
Study Notes
- 2.3 The Periodic Table The periodic table is one of supreme accomplishments of information representation (I'd put the Hertzprung-Russell diagram of stellar characteristics in this category as well). This way of looking at chemical elements allows us to quickly identify a given element by its atomic mass, bonding characteristics, and relative reactivity with other elements. By reactivity, we mean the way that it reacts to form molecular compounds with other elements. By looking at the position of a given element in the periodic table, we can predict many of its characteristics and behaviors.
- The periodic table lays out the known elements in an array that helps explain their individual chemical characteristics and relationships to other elements. We move from top to bottom and left to right in increasing mass and atomic number. Later you will discover how the position of elements are related to their electron configurations and reactivity.
- The names and characteristics of the chemicals are your vocabulary for the year. Time invested now studying the periodic table will pay you. Understand the information given for each element. Note the color coding and the particular characteristics of each type of element (metal, non-metal, metalloids, noble gases).
- Go back and forth between the descriptions of the groups and the periodic table. Be able to give the general characteristics of each group. Understand what an allotrope is.
- 2.4 Molecules, Compounds, and Formulae. Pay attention to definitions: Molecules are any combination of atoms held together by various kinds of bonds. They range from discrete units to ions to metal lattices. The active part of certain organic molecules is called a functional group; this is the part that will form bonds with other organic molecules to make long chains or polymers. You may remember these from biology (hydroxyl, carbonyl, carboxyl, amine).
There are four common representations of molecules.
- Molecular formulae show number of atoms of particular elements in a molecule, but not how specific atoms are grouped or linked to each other.
- Condensed formulae are particularly useful in organic chemistry and show subgroups within the molecule in order.
- Structural formulae are used to show the actual bond connections between atoms, since it is possible for molecules with the same formulae to have different structures (isomers).
- Molecular Models may be portrayed as "ball and stick" models to show 3-dimensional relationships, or as solid models show how the volume is occupied.
- 2.5 Ions and Ionic Compounds. Ions are simply atoms or molecules that have lost or gained electrons. Ionic compounds are held together by the attraction between the oppositely-charged components. The force between components depends on the number of charges involved.
- Monatomic ions: Elements in the same vertical column or group on the periodic table tend to gain or lose electrons in the same way. Study the chart on page 72 and identify the the normal charges on ions for each element in the periodic table groups. You will need to refer back to this table for the homework problems.
- Polyatomic ions: There is only one common polyatomic positive ion — NH4+; all other common polyatomic ions are negative.
Naming conventions allow us to talk about ions and molecules without having to spell out the formulae.
- Hydrated Compounds are dry powder compounds (usually) made of ions that have attracted and arranged water molecules in particular crystalline forms.
- 2.6 Atoms, Molecules, and the Mole. Atoms and molecules interact individually, according to the kinetic molecular theory. But they are so small that we cannot measure reactions between individual atoms; we have to look at measurable masses of the components of a reaction, which means that we need a way to translate grams into numbers of atoms. We determine the molar mass of compounds by adding up the atomic masses of the components.
Important Formulae and Notation
| No Formulae for this Section |
Web Lecture
Read the following weblectures before chat: The Periodic Table
Study Activity
Videos for Chapter 2
Our textbook publisher has a video website at Thinkwell Video Lessons
- Study the layout and rationale behind the Creating the Periodic Table.
- Review the concepts of naming compounds with the three videos under Chemical Nomenclature.
Use the simulation below to explore the relationship between isotopes and atomic mass.
- Click on the option for "Isotopes".
- Click on the PLUS signs to expand the Symbol and Abundance in Nature boxes.
- You start with a hydrogen atom. What happens to the mass number as you add neutrons to it? What happens to the symbol? What happens to the amount of the isotope in nature? Are there any isotopes of hydrogen that don't exist in nature (abundance is 0%)? How does the atomic mass compare with the atomic weight for each isotope?
- Reset (click on orange button with circular arrow in the lower right of the frame) and chose carbon from the periodic table. Reopen the Symbol and Abundance in Nature boxes if they have closed. With carbon-12, what is the atomic mass? Add neutrons and notice what happens to the symbol and abundance amounts. Are there any naturally-occuring C-15 or C-16 isotopes?
- Click on the option for "Mixtures".
- Add four H-1 and one H-2 atoms to the work area. What is the percent composition of the mixture? What is the average atomic mass?
- Add four more H-1 atoms. What happens to the percent composition of H-1 and H-2? What happens to the average atomic mass?
- Click on the slidebar at the bottom left of the work area so that you can add a lot of hydrogen isotopes at once. Can you create a mix that matches natures mix with 100 atoms of each isotope?
- Experiment with nitrogen or carbon. Can you create a mix that is near to the natural mix?
- Experiment with the three isotopes of oxygen and see how changing the isotope percentage changes the average atomic mass.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
Chapter Quiz
- There is no chapter quiz YET.
Lab Work
Lab: Read Illustrated Guide to Home Chemistry Experiments, "Chapter 5: Mastering Lab Skills".
- If you do not have, or cannot afford a chemical balance, construct a simple equal-arm balance using the instructions at at Making a Balance and Performing Calibration.
- Practice basic skills in handling hot equipment safely with the Skills Lab
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