Atoms of each of the following elements are essential for life. Give the group name for the following elements:. In studying the periodic table, you might have noticed something about the atomic masses of some of the elements.
Element 43 technetium , element 61 promethium , and most of the elements with atomic number 84 polonium and higher have their atomic mass given in square brackets. This is done for elements that consist entirely of unstable, radioactive isotopes you will learn more about radioactivity in the nuclear chemistry chapter. An average atomic weight cannot be determined for these elements because their radioisotopes may vary significantly in relative abundance, depending on the source, or may not even exist in nature.
The number in square brackets is the atomic mass number and approximate atomic mass of the most stable isotope of that element. The discovery of the periodic recurrence of similar properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing atomic number in rows known as periods and columns known as groups.
Elements in the same group of the periodic table have similar chemical properties. Elements can be classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1—18 from left to right. Explanation: Periodic Table is based on periodic law which states that if elements are arranged in order of increasing atomic numbers then their properties are repeated in periodic manner. Related questions How can the periodic table be used to predict new elements?
How are the elements are organized in the periodic table? Why is the periodic table a useful tool? How are elements arranged in the modern periodic table? What were the contributions of Mendeleev to the periodic table? Metals lose their valence electrons easily while non-metals gain them easily. As a result, metals are good heat and electricity conductors while non-metals are insulators.
Metals are malleable and solid at room temperature whereas non-metals are brittle and can exist in the solid, liquid or gaseous state.
Most of the elements are either metals or metalloids, which have properties somewhere between metals and non-metals. The elements having the most metallic nature are located in the lower left-hand portion of the chart. Those with the least metallic qualities are in the upper right-hand corner. The bulk of the elements do not fit comfortably into the neat group-and-period arrangement envisioned by Russian chemist Dmitri Ivanovitch Mendeleev , who was the first to develop the periodic table.
These elements, known as the transition elements, occupy the middle of the table, from periods 4 through 7 and between groups II and III. Because they can share electrons in more than one shell, they are not clearly electron donors or acceptors.
This group includes such common metals as gold, silver, iron and copper. In addition, two groups of elements appear at the bottom of the periodic table. They are called the lanthanides and actinides respectively. Here's how it works:.
Even if you don't know anything about a particular element, you can make predictions about it based on its position on the table and its relationship to elements that are familiar to you. For example, you may not know anything about the element osmium, but if you look at its position on the periodic table, you'll see it's located in the same group column as iron.
This means the two elements share some common properties. You know iron is a dense, hard metal. You can predict osmium is also a dense, hard metal. As you progress in chemistry, there are other trends in the periodic table you'll need to know:. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile.
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