6.4: Patterns in the Periodic Table
pg. 220
Key Concepts:
2. Metals and non-metals have characteristic physical properties.
3. Elements are organized according to their atomic number and electron
arrangement on the periodic table.
6. Elements can be both beneficial and harmful to humans and to the
environment.
- The periodic table is arranged in particular pattern.
- All elements in the same column express the same physical and chemical
properties.
- Understanding these patterns allows you to predict the properties of any
element by its location on the periodic table.
Chemical Families
Chemical Family: a column of elements with similar properties on the
Periodic Table.
Alkali Metals: an element in Group 1 of the periodic table.
- Alkali Metals are found in column one of the periodic table. A column is
also known as a chemical family of elements.
- Elements from family one are Lithium (Li), Sodium (Na), and Potassium
(K).
- These metals are soft, slivery, shiny, and are very reactive.
Alkaline Earth Metal: an element in Group 2 of the periodic table.
- Alkaline Earth Metals are elements found in family two, such as;
Beryllium, (Be), Magnesium (Mg), and Calcium (Ca).
- These metals are shiny and silvery, but are not soft. Alkaline Earth Metals
are very reactive also.
Noble Gas: an element in Group 18 of the periodic table.
- Elements that are noble gases are found in family number eighteen, the
extreme right column.
- Elements in column 18 are stable and non-reactive.
- Examples of noble gases are, helium (He), Neon (Ne), and argon (Ar).
Halogen: an element in Group 17 of the periodic table.
- Halogens are found in column number seventeen.
- Halogens are non-metals, they are very reactive, and they like to react with
metals in families one and two.
- Fluorine (F), chlorine (Cl), and bromine (Br) are examples of Halogens.
Periodic Trends
Period: a row on the periodic table.
- Elements found in the same horizontal row of the periodic table increase in
reactivity and decrease in reactivity.
- Group one metals, are more reactive then group two metals. Decrease in
reactivity as you move to the right.
- Group 17 elements are more reactive then elements found in group 16.
- Horizontal rows are known as Periods, and refer to cycles and are
reacquiring.
History of the Periodic Table
- In 1869 Dmitri Mendeleev developed the first periodic table.
- At this time there were only 63 known elements.
- Elements were arranged first by increasing mass.
- He noticed patterns and placed elements with similar properties together.
- Elements with similar properties were placed under each other, with the
lightest mass above.
- His table when completed had number of empty spaces. From this
Mendeleev determined that there were missing elements that had yet to be
discovered.
Figure 8: Mendeleev left blank spaces in this periodic table for elements that
had not yet been discovered.
Evidence of Learning: Students can …
- recognize the characteristic properties of common families on the periodic
table.
- name some of the chemical families on the periodic table.
- distinguish between a period and a family on the periodic table.
- locate elements on the periodic table.
- understand how Mendeleev used the properties of elements to organize
them in the periodic table.
Check Your Learning:
Questions 1 – 11, page 225
Summary:
- A chemical family is a column of elements on the periodic table.
- Elements in the same chemical family have similar properties.
- The first two families of the periodic table are the alkali metals and the
alkaline earth metals.
- The last two families on the periodic table are the halogens and the noble
gases.
- A period is a row on the periodic table.
- Mendeleev grouped elements with similar physical and chemical properties
in the same column in a periodic table.
- Mendeleev correctly predicted the properties of elements that had not yet
been discovered.