Main-group elements periodic patterns

The pattern of ion formation by main-group elements can be summarized by a single rule for atoms toward the left or right of the periodic table, atoms lose or gain electrons until they have the same number of electrons as the nearest noble gas atom. Thus, magnesium loses two electrons and becomes Mg2+, which has the same number of electrons as an atom of neon. Selenium gains two electrons and becomes Se2, which has the same number of electrons as krypton. We shall discover the origin of this rule in Section 2.3. 

You have seen that the structure of the periodic table is directly related to energy levels and arrangements of electrons. The patterns that emerge from this relationship enable you to predict the number of valence electrons for any main group element. They also enable you to predict the number of energy levels that an element s electrons occupy. The relationship between electrons and the position of elements in the periodic table leads to other patterns, as well. You will examine several of these patterns in the next section. 

Patterns in chemical reactivity of the elements correlate with patterns in the physical structure of the atom they are both periodic functions of Z. Reading across the periodic table (horizontally) shows that each main-group element (Groups I-VIII) in Period 3 has exactly 8 more electrons than the element immediately above it in Period 2. Similarly, each main-group element in Periods 4 and 5 has exactly 18 more electrons than the corresponding element in the period above. The sequence of numbers, 8, 8, 18, 18, and so forth, that organize the periodic table into groups (columns), whose elements have similar physical and chemical properties, arises from the quantum theory of atomic structure (see discussion in Chapter 5). 

The pattern metal-metalloid-nonmetal-noble gas is typical for the main group elements in each period. Period 2 begins with a metal, lithium, and ends with a noble gas, neon. In between are the metal beryllium the metalloid boron and the nonmetals carbon, nitrogen, oxygen, and fluorine. Remember that the most active metals. Groups 1 and 2, are in the s region of the periodic table. The metalloids, nonmetals, and less active metals are in the p region of the periodic table. 

Patterns of Behavior of Main Group Elements The Main Group Metals and Nonmetals MiniLab 8.1 What s periodic about atomic radii ... 

The main group elements show a periodic pattern of oxidation states. For the first 25 elements, there is a stepwise increase in the oxidation state for the elements as you follow them going across the periodic table, left to right, as shown in Figure 3-1. The maximum oxidation state of an element is equal to the number of electrons in the outer orbital for these first 25 elements. 

Chapter 14 Periodic Patterns in the Main-Group Elements... 

Knowledge of the 90 chemical elements and their properties in compounds led to the construction, by man, of a unique table of elements, the Periodic Table, of 18 Groups in six periods in a pattern fully explained by quantum theory, described in Chapter 2. There is then a huge variety of chemical combinations possible on the Earth and limitations on what is observable are related to element position in this Table. It also relates to the thermodynamic and/or kinetic stability of particular combinations of them in given physical circumstances (Table 11.3). The initial state of the surface of the Earth with which we are concerned was a dynamic water layer, the sea, covering a crust mainly of oxides and some sulfides and with an atmosphere of NH3, HCN, N2, C02(C0, CH4), H20, with some H2 but no 02. This combination of phases and their contents then produced an aqueous solution layer of particular components in which there were many concentration restrictions between it and the components of the other two layers due to thermodynamic stability, equilibria, or kinetic stability of the chemicals trapped in the phases. It is the case that equilibrium... 

An atom is the smallest particle of an element that still has all the properties of that element. Atoms are made up of three main particles. Protons and neutrons come together in an atom s nucleus, whereas electrons orbit the nucleus. The number of protons in an atom determines what type of element it is. The structure of the periodic table comes from the fact that electron shells are filled in a specific pattern. The rows of the table are called periods and the columns are called groups. There are other ways to divide up the table, as well. 

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