Term
| The Modern Periodic Table |
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Definition
The modern Periodic Table, based on
Mendeleev’s design, allows us to include all of these classifications in one model.
It is a model that chemists use to explain and predict the chemical
and physical behaviour of the elements. |
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Term
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Definition
One way is to separate them by their physical properties into metals, metalloids, and non-metals.
Another way to classify the elements is by family, based on common
physical and chemical properties.
The elements can also be classified according to their ion charges, atomic
number, or electron arrangement. |
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Term
| Finding Information in the Periodic Table |
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Definition
Examine the following sample entry below from the Periodic Table (Figure 3).
Note the location of the element name, chemical symbol, atomic number,
ion charge, and atomic mass. |
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Term
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Definition
The atomic mass of an element is the average of the mass numbers of all the naturally occurring isotopes.
The mass number is the mass of one
particular isotope of an element. You can determine the mass number of
the most common form of an element by rounding the atomic mass to the
nearest whole number. |
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Term
| Calculating the Number of Electrons in an Ion |
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Definition
The number of protons in the nucleus of an atom does not change when the atom forms an ion—only the number of electrons orbiting the nucleus can change.
The size of the ion charge tells you the difference between the number of
protons and the number of electrons in the ion. The or sign tells you if
there are fewer (+) or more (-) electrons than protons
Aluminum’s atomic number is 13, so its atoms have 13 protons. Aluminum’s
ion charge is 3. Therefore, an atom of aluminum has 13 electrons. An ion of
aluminumwill have only 10 electrons, 3 fewer electrons than protons. Oxygen’s
atomic number is 8, and its ion charge is 2. |
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