9. Select three elements that are in the same period in the Periodic Table of Chemical Elements by D. I , Mendeleev , and arrange the selected elements in ordér of increasing metallic properties. 1) Ca 2) Al 3) Se 4) Sn 5)Ge Answer (score:1):

The three elements that are in the same period in the Periodic Table of Chemical Elements by D. I. Mendeleev are:<br /><br />1) Aluminum (Al)<br />2) Germanium (Ge)<br />3) Calcium (Ca)<br /><br />Arranging these elements in order of increasing metallic properties, we get:<br /><br />1) Aluminum (Al)<br />2) Germanium (Ge)<br />3) Calcium (Ca)