The Periodic Table Section 1 Recognizing a Pattern How did Mendeleev arrange the elements in his periodic table? In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass.
The Periodic Table Section 1 Recognizing a Pattern, continued Mendeleev was able to predict new elements. Mendeleev left spaces in his table to make the pattern fit. He used the spaces to successfully predict the existence and properties of elements not yet discovered. A few elements did not fit the pattern.
The Periodic Table Section 1 Changing the Arrangement How are elements arranged in the modern periodic table? The modern periodic table organizes elements by atomic number. When the elements are arranged in this way, elements that have similar properties appear at regular intervals.
The Periodic Table Section 1 Changing the Arrangement, continued As scientists learned more about the structure of the atom, they improved Mendeleev s table. Arranging the table by atomic number (number of protons) rather than by atomic mass fixed the discrepancies in Mendeleev s table. periodic law: the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements
The Periodic Table Section 1 The Periodic Table of the Elements
The Periodic Table Section 1 Changing the Arrangement, continued Elements become less metallic across each period. period: a horizontal row of elements in the periodic table Elements in a group have similar properties. group: a vertical column of elements in the periodic table; elements in a group share chemical properties
The Periodic Table Section 2 The Role of Electrons Why do elements within a group of the periodic table have similar chemical properties? The periodic trends in the periodic table are the result of electron arrangement.
The Periodic Table Section 2 The Role of Electrons, continued Valence electrons account for similar properties. An element s location in the periodic table is related to electron arrangement. Example: Lithium and sodium, in Group 1, each have one valence electron.
The Periodic Table Section 2 Ion Formation What happens to an atom that gains or loses electrons? If an atom gains or loses electrons, it no longer has an equal number of electrons and protons. Because the charges do not cancel completely, the atom has a net electric charge.
The Periodic Table Section 2 Ion Formation, continued Group 1 elements form positive ions. The single valence electron is easily removed. Group 17 elements form negative ions. The addition of one valence electron fills the outer energy level.
The Periodic Table Section 2 How Are Elements Classified? What are the three main categories of elements? All elements are either metals, nonmetals, or semiconductors.
The Periodic Table Section 2 How Are Elements Classified?, continued Elements in each category have similar properties. metal: an element that is shiny and that conducts heat and electricity well nonmetal: an element that conducts heat and electricity poorly semiconductor (or metalloid): an element or compound that conducts electric current better than an insulator does but not as well as a conductor does
The Periodic Table Section 2 How Are Elements Classified?, continued
The Periodic Table Section 3 Classifying Elements Further What does each element family have in common? In general, the elements in a family have the same number of valence electrons.
The Periodic Table Section 3 Metals What are the families of metals? Families of metals include the alkali metals, the alkaline-earth metals, and the transition metals. alkali metal: one of the elements of Group 1 of the periodic table alkaline-earth metal: one of the elements of Group 2 of the periodic table transition metal: one of the metals that can use the inner shell before using the outer shell to bond
The Periodic Table Section 3 Metals, continued The alkali metals are very reactive. Alkali metals are in Group 1, on the left edge of the periodic table. They are reactive because they have one valence electron that is easily removed. They are soft and shiny, and many have similar melting points, boiling points, and densities.
The Periodic Table Section 3 Metals, continued Alkaline-earth metals form compounds that are found in limestone and in the human body. Alkaline-earth metals are in Group 2. Alkaline-earth metals are less reactive than alkali metals, but still react to form positive ions. In general, alkaline-earth metals are harder, denser, stronger, and have higher melting points than alkali metals.
The Periodic Table Section 3 Metals, continued Transition metals are in the middle of the periodic table. With the exception of mercury, transition metals are harder, more dense, and have higher melting points than alkali metals and alkaline-earth metals. They are also less reactive, but they can form positive ions.
The Periodic Table Section 3 Nonmetals What are some of the families of nonmetals? Families of nonmetals include the noble gases and the halogens. noble gas: one of the elements of Group 18 of the periodic table halogen: one of the elements of Group 17 of the periodic table
The Periodic Table Section 3 Nonmetals, continued The noble gases are relatively inert. The noble gases are in Group 18. They exist as single atoms instead of as molecules. They are inert, or unreactive, because their s and p orbitals are filled. In general, they do not form ions or compounds.
The Periodic Table Section 3 Nonmetals, continued The halogens combine easily with metals to form salts. The halogens are in Group 17. With the addition of a single electron, halogens become stable. They combine easily with metals (especially alkali metals) to form salts.
The Periodic Table Section 3 Nonmetals, continued Nonmetals and their compounds are plentiful on Earth. Six other nonmetals are on the right side of the periodic table. Carbon can form many compounds. There are millions of carbon-containing compounds.
The Periodic Table Section 3 Semiconductors What are semiconductors? As their name suggests, semiconductors are able to conduct heat and electricity under certain conditions.