“Breaking the Code” Homework
1. Read the following passages for homework. Then complete the exercises at the end.
There are somewhere around 110 elements total - 91 of them are found in nature. The rest of the elements have
mostly been created in the laboratory. Even though the entire world, and all its objects, and all its creatures are made
up out of the elements, the average person is probably familiar with only about 30 of the elements. Some of the
elements are very rare or have only existed for very short periods of time. The element called Einsteinium, number 99,
was discovered in the radioactive debris of a hydrogen bomb test in the Pacific Ocean in 1952.
The elements of the periodic table are organized into two basic groups—metals and nonmetals. Most of the elements
in the entire periodic table are metals. Often there is a stair step line on the periodic table showing the diving line
between metals and nonmetals.
Nonmetals are poor conductors of heat and electricity. They are located in the upper right hand portion of the table.
The include the eleven elements that are found as gases in their natural state. The other nonmetals are usually brittle
solids.
The metals, on the other hand, are excellent conductors of heat and electricity. They are generally shiny and malleable
(bendable). Most of the elements in the periodic table are classified as metals. Copper is a typical metal. It is shiny,
bends easily, is an excellent conductor of electricity, and is commonly used for electrical wires. Metals are located on
about 3/4 or more of the periodic table—on the left.
Some of the elements do not belong clearly to either classification. These elements are called metalloids. They have
properties of both metals and nonmetals. The metalloids are located somewhere along the stair step line between
metals and nonmetals. Some periodic tables classify the metalloids with the nonmetals.
The columns in the periodic table are called groups. Sometimes they are also called families. All the groups have
similar properties, which you probably noticed during your card sort. We have only included the names of the most
significant groups in our periodic table (such as the alkaline earth metals and the noble gases). There is more than one
numbering system for the groups. Some periodic tables number the groups straight across from 1 to 18. Some number
the groups the way we have.
The alkali metals are in Group 1 of the table. They have very similar properties. They are highly reactive, and are
never found as free metals in their natural state. In other words, they are always found combined with other elements in
the form of compounds. When the elements in this group combine with chlorine they always combine in a ratio of 1:1
to form a new compound. For example, Na bonds with Cl to form NaCl.
The alkaline earth metals are in Group 2 of the table. They also have similar properties. The elements in this group
combine with chlorine in a ratio of 1:2 to form a new compound. For example, Mg bonds with Cl to form MgCl2.
The halogens are in Group 7 (second to the last column) of the table. The elements in this group combine with
hydrogen in a ratio of 1:1 to form a new compound. For example, F bonds with H to form HF.
The noble gases are in Group 8 (the very last column) of the table. They are all gases and are extremely unreactive.
They do not combine with other elements to form new compounds under normal conditions. They have also been
called the inert gases. Some periodic tables classify the noble gases as nonmetals while others simply refer to the
noble gases as a group unto themselves.
The seven rows going across the table are called periods. The easy reference the periods are numbered one through
seven going down the left hand side of the table. The word periodicity refers to the reoccurring patterns, which repeat
over and over again in the table. As you get to know the periodic table these various patterns will become clearer.
The lanthanides and the actinides are organized in rows, not columns. They are found in the 6th and 7th periods (not
the 8th and 9th). They are normally shown below the periodic table mainly for convenience. The lanthanides are also
called the rare earth elements although they are not considered particularly rare anymore except for promethium, Pm,
which is created artificially. The element lanthanum, La, is included in the lanthanides by most periodic tables and
accounts for the name of this set of elements. Similarly, the element Ac, actinium, is included in the actinides, and
gives this set of elements their name. The actinide series of the elements are all radioactive. Only the first four have
been found in nature. The rest have been created synthetically. The synthetic actinides are often referred to as the
transuranium elements.
2. On your periodic table (one of the tables you printed out for HW-not the periodic table I gave you in class), clearly
label the alkali metals, the alkaline earth metals, the halogens and the noble gases.
3. Label the lanthanides, actinides, and the transition metals.
4. Name two elements that would have properties similar to beryllium, with atomic weights higher than 130.
5. Name all the halogens.
6. Name three transition metals.