محاضره 3 احياء نظري د رياض.pdf

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ Atoms and Subatomic Particles An atom is the smallest quantity of an element that retains the unique properties of that element. In other words, an atom of hydrogen is a unit of hydrogen—the smallest amount...

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ Atoms and Subatomic Particles An atom is the smallest quantity of an element that retains the unique properties of that element. In other words, an atom of hydrogen is a unit of hydrogen—the smallest amount of hydrogen that can exist. Atomic Structure and Energy Atoms are made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. The number of positively-charged protons and non-charged (“neutral”) neutrons, gives mass to the atom, and the number of each in the nucleus of the atom determine the element. The number of negatively-charged electrons that “spin” around the nucleus at close to the speed of light. 1 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ Atomic Number and Mass Number The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of every atom of that element. The atomic number uniquely identifies a chemical element. It is identical to the charge number of the nucleus. In an uncharge atom, the atomic number is also equal to the number of electrons. The periodic table also known as the periodic table of (the) (chemical) elements, is a tabular display of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of chemistry. It is a graphic formulation of the periodic law, which states that the properties of the chemical elements exhibit a periodic dependence on their atomic numbers. The periodic table continues to evolve with the progress of science. In nature, only elements up to atomic number 94 exist; to go further, it was necessary to synthesise new elements in the laboratory. Today, all the first 118 elements are known. 2 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ the elements can be classified as metals, nonmetals, or metalloids. -Metals are good conductors of heat and electricity, Most of the metals are solids at room temperature, with a characteristic silvery shine (except for mercury, which is a liquid). -Nonmetals are (usually) poor conductors of heat and electricity, many of the elemental nonmetals are gases at room temperature, while others are liquids and others are solids. 3 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ -metalloids are intermediate in their properties. In their physical properties, they are more like the nonmetals, but under certain circumstances, several of them can be made to conduct electricity. These semiconductors are extremely important in computers and other electronic devices. Groups and periods       The rows of the table are called periods, and the columns are called groups. The periodic table is made up of columns called groups horizontal lines called periods different regions of the table known as blocks. The groups are responsible for more significant trends than periods; within the same groups there are present the same electronic configurations in their outer most shell. This is one of the main reasons as to why a group with the same number of outermost 4 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 3 ‫كليه الطب‬   ‫قسم الكيمياء الحيوية والطبية‬ electrons will have similar chemical properties; for example the halogens (group 7) have seven electrons in their outer shell, they are all so determined to accept an electron to complete their outer shell. This allows the elements within group 7 to show similar properties. i.e Groups - Columns in the periodic table, the elements in a group show similar properties and are responsible for identical trends. Elements from the same column group of the periodic table show similar chemical characteristics Periods - Are the horizontal lines across the periodic table, they also represent the number of shells an element has, for example a period 2 element will have 2 shells. Blocks - There are in theory 5 differnet blocks in the periodic table: 5 ‫جامعه وارث االنبياء‬ ‫د رياض حنيوه‬ ‫كليه الطب‬ ‫‪lecture 3‬‬ ‫قسم الكيمياء الحيوية والطبية‬ ‫‪s-block,‬‬ ‫‪p-block,‬‬ ‫‪d-block,‬‬ ‫‪f-block‬‬ ‫‪and g - block‬‬ ‫‪6‬‬ ‫جامعه وارث االنبياء‬ ‫د رياض حنيوه‬ ‫كليه الطب‬ ‫‪lecture 3‬‬ ‫قسم الكيمياء الحيوية والطبية‬ ‫‪END OF LEC 3‬‬ ‫‪7‬‬