GEN-CHEM-1-LESSON-3-FINALS PDF

LESSON3 ARRANGEMENT OF ELEMENTS IN THE PERIODIC TABLE  “PERIODIC” Occurring or recurring at regular intervals. Happening repeatedly although not necessarily frequently  Thus arrangement of the elements in the periodic table shows the patterns or trends of the properti...

LESSON3 ARRANGEMENT OF ELEMENTS IN THE PERIODIC TABLE  “PERIODIC” Occurring or recurring at regular intervals. Happening repeatedly although not necessarily frequently  Thus arrangement of the elements in the periodic table shows the patterns or trends of the properties.  GROUP or FAMILY A vertical column of elements. Elements in the same group often have similar chemical and physical properties.  Group A (IA-VIIA) Composed of Representative Elements and Noble Gas Family. The name comes from the fact that these elements are unreactive towards other elements or compounds. (8 electrons in the outer shell) It is called representative elements because the number of an element represents or is equal to the number of valence electron. Group B (IB-VIIIB, Lanthanides, Actinides) Includes transition metals, Lanthanides, and Actinides. Lanthanides - atomic numbers 57 to 71. Actinides - atomic numbers 89 to 103 Transition Metals – connect the left and right sides of the periodic table.  Note: The periodic number of an element (horizontal arrangement) corresponds to the highest energy level occupied by an element’s electron. e.g. K Potassium has an atomic number of 19. Electron configuration: 1s2 2s2 2p6 3s2 3p6 4s1  PERIOD or SERIES A horizontal row of elements. Have varying physical and chemical properties.  Elements arranged vertically in the periodic table fall into two big groups, namely, group A and group B. TRENDS & PERIODIC VARIATION OF THE PROPERTIES OF ELEMENTS IN THE PERIODIC TABLE  Arrangement of elements in the periodic table is significant in determining the properties of elements within a group.  IONIZATION ENERGY Energy needed to remove an electron from an atom or ion in its ground state. During the removal of electrons, one electron is removed from the atom at a time. Energy needed to remove the first valence electron from an atom is called the first ionization energy.  In general Ionization energy tends to increase from bottom to the top, and increase from left to right.  Metals have lower ionization energies than nonmetals Nonmetals have higher IE because their atomic radii are smaller.  The case of giving up electrons determines the reactivity of an atom. Valence electrons in big atoms are easily given up because they are farther away from the nucleus. Shielding Effect – first few main energy level act as a shield of valence electrons from the nuclear force.  ELECTRON AFFINITY Refers to the change in energy when an atom in its ground state gains an electron forming an anion. Nonmetals always form an anion because they have high electron affinity.  In general Electron affinity increases from left to right across a period, and decreases from top to bottom within a group.  ELECTRONEGATIVITY (EN) Ability of an atom in a chemical bond to attract electrons toward itself and is usually measured in electron volt (ev). The higher the Ea, the greater the ability of an atom to pick up electrons.  In general Electronegativity increases from left to right across a period, and decreases from top to bottom within a group.  Metallic & Nonmetallic Characters Metallic Character – Metallic elements are those that can loose electrons and form positive ions (cation). Increases from top to bottom, and decreases from right to left.  Metallic & Nonmetallic Characters Nonmetallic Character – Nonmetal elements that can gain electrons and form negative ions (anion). Increases from bottom to the top, and increases from left to right.