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A nonmetal is typically dull and a poor conductor of electricity and heat. Metals are also malleable (they can be beaten into thin sheets) and ductile (they can be drawn into thin wires). (b) Covalent radii of the elements are shown to scale. The atomic radius for the halogens increases down the group as n increases. A metal is a substance that is shiny, typically (but not always) silvery in color, and an excellent conductor of electricity and heat. 1: (a) The radius of an atom is defined as one-half the distance between the nuclei in a molecule consisting of two identical atoms joined by a covalent bond. We know that as we scan down a group, the principal quantum number, n, increases by one for each element.\). General trends noted are increasing circle size moving from top to bottom in a group, with a general tendency toward increasing atomic radii toward the lower left corner of the periodic table. No spheres are provided for the noble or inert gas, group 18 elements. Beneath the molecule is the label, “I radius equals 266 p m divided by 2 equals 133 p m.” In figure b, a periodic table layout is used to compare relative sizes of atoms using green spheres. Apply the rule of the periodic table to your element. The distance between the radii is 266 p m. Beneath the molecule is the label, “B r radius equals 228 p m divided by 2 equals 114 pm.” The fourth diatomic molecule is in purple. The distance between the radii is 228 p m. Beneath the molecule is the label, “C l radius equals 198 p m divided by 2 equals 99 pm.” The third diatomic molecule is in red.
![periodic table periodic table](http://biotech.fyicenter.com/Molecule/Valence-Electrons-Shown-in-Periodic-Table.png)
The distance between the radii is 198 p m. The second diatomic molecule is in a darker shade of green. Beneath the molecule is the label, “F radius equals 128 p m divided by 2 equals 64 p m.” The next three models are similarly used to show the atomic radii of additional atoms. The distance between the centers of the two atoms is indicated above the diagram with a double headed arrow labeled, “128 p m.” The endpoints of this arrow connect to line segments that extend to the atomic radii below. Two spheres are pushed very tightly together. Identify elements that will have the most similar properties to a given element. The first model, in light green, is used to find the F atom radius. Explain the relationship between the chemical behavior of families in the periodic table and their valence electrons. The electronic configuration of each element is decided by the Aufbau principle which states that the electrons fill orbitals in order of increasing energy levels. Transition Metals: Groups 3-12 - d and f block metals have 2 valence electrons. Alkaline Earth Metals: Group 2 (IIA) - 2 valence electrons. In figure a, 4 diatomic molecules are shown to illustrate the method of determining the atomic radius of an atom. Another common method of categorization recognizes nine element families: Alkali Metals: Group 1 (IA) - 1 valence electron. The general trend is that radii increase down a group and decrease across a period. \): (a) The radius of an atom is defined as one-half the distance between the nuclei in a molecule consisting of two identical atoms joined by a covalent bond. Valence electrons are the electrons in the outermost shell, or energy level, of an atom.