Across 1. Dobereiner: He was a German chemist who is best known for work that foreshadowed the periodic law for the chemical elements, and for inventing the first lighter, which was known as the Dobereiner's lamp. 2. Newlands: He was a British chemist who worked concerning the periodicity of elements. He was the first person to devise a periodic table of chemical elements arranged in order of their relative atomic masses. 5. Eight: A period in the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. 10. Bismuth: It is a chemical element with a symbol Bi and atomic number 83 . It is a post-transition metal and one of the pnictogens with chemical properties resembling its lighter group 15 siblings arsenic and antimony. 11. Argon: It is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. 13. Oxygen: Its atomic number is 8. It is a member of the chalcogen group in the periodic table, a highly reactive non-metal. 14. Calcium: Its symbol is Ca with an atomic number 20 . As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. 16. Helium: Its symbol is He and atomic number is 2 . It is a monatomic gas and first in the noble gas group in the periodic table.19. Nitrogen: It is a non-metal and the lightest member of group 15 of the periodic table, often called the pnictogens. 19. Nitrogen: Its symbol is N and atomic number is 7. It is about 78 % in the air. It is a non-metal and lightest member of group 15 of the periodic table. Down 3. Mendeleev's: He was a Russian chemist and inventor. He is best known for formulating the Periodic Law and creating a farsighted version of the periodic table of elements. 4. Moseley: He was an English physicist whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. 6. Third: Magnesium with a symbol Mg and atomic number 12 . It has three valence shells. The electronic configuration is 2 , 8 , 2 . The valency is 2. 7. Fourteen: The element with atomic number 14 belongs to 14 th group. Its electronic configuration is 2 , 8 , 4 . The elements in this group have four valence electrons. 8. Bromine: It is a non-metal exists as a liquid at room temperature. Its symbol is Br with an atomic number 35 . It is a third-lightest halogen. 9. Two: The electronic configuration of an element with atomic number 20 is 2 , 8 , 8 , 2 . So, its valency is 2 . It has four shells and belongs to the fourth period. 12. Silicon: The metalloid in the third period is silicon. Its atomic number is 14. The electronic configuration is 2 , 8 , 4 . It has three shells and belongs to the third period and group fourteen. Its properties are intermediate between those of metals and solid non-metals or semiconductors. 15. Sodium: It combines with chlorine to form common salt. Its atomic number is11. It is an alkali metal, being in group1 of the periodic table. Its electronic configuration is 2 , 8 , 1 . 17. Gold: It is a chemical element with the symbol Au (from Latin: aurum ) and atomic number 79, making it one of the higher atomic number elements that occur naturally. 18. Chlorine: It is a chemical element with the symbol Cl and atomic number 17. It is used in sterilisation of drinking water. 20. Fluorine: It is a chemical element with the symbol F and atomic number 9. Its electronic configuration is 2 , 7 . It is the most electronegative element. It is a diatomic halogen gas.

Science Chemistry>Chapter 5 - Periodic Classification of Elements>ASSESSTMENT

A K Srivastava Solutions for Chapter: Periodic Classification of Elements, Exercise 1: ASSESSTMENT

Author:A K Srivastava

A K Srivastava Chemistry Solutions for Exercise - A K Srivastava Solutions for Chapter: Periodic Classification of Elements, Exercise 1: ASSESSTMENT

Attempt the practice questions on Chapter 5: Periodic Classification of Elements, Exercise 1: ASSESSTMENT with hints and solutions to strengthen your understanding. Science Chemistry solutions are prepared by Experienced Embibe Experts.