Properties of elements - Periodicity of properties
You now have some sense that the arrangement of the periodic table is connected with the order of atomic numbers. However, what about the characteristic properties of the elements? Is there any link between the properties of the elements and the way elements are arranged in the periodic table?
All elements in the Periodic Table can be split into three main categories: Metals, Nonmetals, and
Metalloids (semi-metals).
All metals share certain characteristic properties, which are common to all metals.
All nonmetals share certain characteristic properties that are common to all nonmetals.
Metalloids possess properties common to both metals and nonmetals.
Now, how can you locate the elements belonging to a particular category?
Seven elements, located along the “staircase” (step) line, are metalloids. Those elements are B, Si,
Ge, As, Sb, Te, Po . Please find them in your table of elements
The elements located to the left of the “staircase” line are metals. As you see, the majority of elements are metals.
Please find them in your table
The elements that lie to the right of the step line, are nonmetals.
Please locate them in your table
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Properties of Metals a) High Reactivity: majority of metals react with acids b) Metallic Luster: property of reflecting light that gives the materials shiny appearance c) Good thermal conductivity: they possess a good ability to conduct heat. Metals are cold to the touch because they draw heat from your skin. The heat moves along the metal very well, going away from your skin. d) Good electrical conductivity, which is the ability to conduct electricity. They allow electric current to pass through them, so we say that metals are good electrical conductors e) Metals are malleable; malleability is the ability of materials to be hammered or bent into different shapes. If a material breaks when you try to change its shape, it’s likely a nonmetal
Generally, the metals become more reactive, as we move down a particular group (family), and as we move from right to left within a particular period
Properties of Nonmetals
Properties of nonmetals are opposite to those of metals (see properties of metals on this page above)
Generally, the nonmetals become more reactive, as we move up a particular group (family), and as we move from left to right within a particular period
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Properties of Metalloids
Metalloids share some properties of both metals and nonmetals
They may or may not conduct electric current (their electric conductivity depends very much on temperature; and, unlike metals, the conductivity improves with temperature)
They do not react with acids
They may or may not have metallic luster
They are poor thermal conductors
They are not malleable
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Additional classification
In addition to the three categories described above, elements located in specific groups (families) are given special names due to their very pronounced, distinctive characteristics.
1) Elements of the first group (1 st
vertical column) are called alkali metals because they react violently upon contact with water, forming an alkali, or base.
Because of their high degree of reactivity, we store them in oil. They must never be handled with bare hands because they will burn skin
(there is a thin layer of water on the surface of your skin!). These elements are soft (you can cut them with a knife!), very light, and melt at a low temperature . Because of their high reactivity, in nature they are never found as free elements, but are always combined with other elements.
Find and list the alkali metals (use the table of elements)
2) Elements of the second group (2 nd
vertical column) form a family of alkaline earth metals . Just like the elements from the first group, they are called alkaline, since in solutions the elements of this group possess alkaline properties. They are called “earth”, since the elements of the group are found in the composition of quite a number of rocks in nature . In their properties, the elements are similar to those of the first group, although the properties are slightly different from those in the first group. For example, they are not as soft, they have less violent reactions, and their melting points are higher than those of alkali metals . Find and list the alkaline earth metals
3) Metals lying to the right of the second group are called transition metals, or sometimes, typical metals. They have high melting and boiling points (temperatures) , that is, very high temperatures are required to melt and boil them. Compared to alkaline metals, the transition metals are hard and dense, while their compounds are mostly coloured (gold, for example) . The typical metals behave more like metals we are used to see around us
4) Halogens make up the second-to-last column of the periodic table . These are coloured substances with distinctly nonmetallic properties. These elements are so reactive that in nature they exist only in combination with other elements. In combination with other elements, they form salts (when combined with alkali metals), and strong acids (when combined with hydrogen). Halogens are toxic, corrosive, and bactericidal (so they are used as antiseptics, and to disinfect water)
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5) Inert gases (also called noble gases) make up the group of elements found in the last column of the periodic table. Inert gases are colourless in their natural state. However, the property that distinguishes them is their almost complete lack of chemical reactivity.
Under ordinary conditions, these gases do not form compounds with other elements because they do not react with them
Questions
1) Identify the chemical category (family) that corresponds to the following elements a) elements that have virtually no chemical reactivity b) the most reactive metallic elements c) metallic elements with relatively low melting temperatures d) relatively rare gases e) most reactive nonmetals
2) Name the element: a) the least reactive alkali metal b) most reactive halogen c) halogen used in fluoridation of water d) Halogen used in disinfection of swimming pools e) halogen added to table salt f) alkaline earth metal possessing the fewest electrons g) Halogen used in disinfection of swimming pools h) alkaline earth metal which is the most important to live organisms
3) Which of the properties of metalloids resemble those of: a) Metals? b) Nonmetals? c) Both metals and nonmetals?
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4) Find the melting temperature of Mercury. How is it different from the melting temperatures of other metals?
How does it make Mercury different from other metals?
5) Judging by their melting and boiling points (temperatures), which of the halogens are gases, which are liquids, and which are solids at a room temperature? Do the research on your own
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