True or false a. Mendeleyev discovered that when elements are arranged in order of increasing atomic weight, certain sets of properties recur periodically. b. Main-group elements are only those in the columns 3A to 8A of the Periodic Table. c. Nonmetals are found at the top of the Periodic Table, metalloids in the middle, and metals at the bottom. d. Among the 118 known elements, there are approximately equal numbers of metals and nonmetals. e. A horizontal row in the Periodic Table is called a group. f. The Group 1A elements are called the “alkali metals.” g. The halogens are Group 7A elements.
Answers
Answer:
The true and false for the above statements are given below with a correct description:
a. True
Mendeleev was a Russian chemist from Petersburg. He gave the periodic table a new definition by developing the periodical classification of elements in the table.
b. False
Correction: The elements of groups 1A and 2A along with elements of groups 3A to 8A are all termed as the main group elements of the periodic table. The main group elements belong to the s-block and p-block.
c. False
Correction: Metallic character increases down a group and nonmetallic character increases across a period on moving left to right. Hence, nonmetals are on the top right of the periodic table, metals on the left of the table, and metalloids are located in between them, which forms the diagonal separation between metals and nonmetals.
d. False
Correction: There are more metals than nonmetals in the periodic table as metals occupy the left part of the table and also the metallic character increases on moving down so nonmetals are less in number, they occupy the upper right part of the table.
e. False
Correction: The horizontal rows in a periodic table are called periods and vertical columns are called groups.
f. True
g. True
Group 7A elements are also called halogens as they are salt-producing elements.