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Atoms are particles of elements. Atoms combine to form compounds. |
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Atoms |
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An atom is the smallest particle of an element that still has the properties of the element. Atoms of one element are different from atoms of other elements. Atoms are too small to be seen even with a microscope. The properties of atoms determine the properties of an element and how the element can combine with other elements. |
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The atom's center, or nucleus, usually has both neutrons and protons. A neutron has no electrical charge. A proton has a positive charge. An atom is identified by the number of protons it has. For example, all carbon atoms have six protons. No other kind of atom has six protons. |
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Electrons move around the protons and neutrons. An electron has a negative charge. Electrons may join or leave atoms, or be shared between atoms. |
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Elements are organized in a table called the periodic table of elements. The elements are arranged in each row according to the number of protons. Larger atoms are on the right side of each row. The columns of the table are arranged so that the elements in each column have similar chemical properties. Therefore, you can predict the properties of an element if you know its column. For example, in the last column on the right you will find elements known as noble gases. All these elements are gases at room temperature. They do not often combine with other elements. |
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Every element has a symbol of one, two, or three letters. Only the first letter of the symbol is capitalized. What elements have the symbols C, H, and Ca? |
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| All helium atoms have exactly 2 protons and usually have 2 neutrons and 2 electrons. |
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| The elements in this column can easily lose one electron each. |
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Nonmetals do not
conduct electricity well. |
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| The lights in this sign contain neon. |
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| Phase at room temperature |
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Gas |
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Not found
in nature |
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Liquid |
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Solid |
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| 1. |
Describe the periodic table and how it is organized. |
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2. |
Predict Use the table to predict what atoms would have similar
chemical properties as calcium. Write their names. |
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