Скачать или смотреть class 10 science ch 5 Most Important Questions for board exam (part-1)🎯

Answers👇

Ans 1- Sodium(Na) (2,8,1).It has 1 electron in valence shell with valency 1.

Ans 2- Long form of periodic table is regarded better than Mendeleev's periodic table due to the following reasons:
1- It is based upon atomic number which is considered better than the atomic mass because the properties of the elements are related to the atomic number.
2- It explain why the elements placed in a group show similar properties but mendeleev's periodic table gives no explanation for the same.
3- All groups in the periodic table are independent groups and there are no sub- groups as in Mendeleev's periodic table.
4- Many defects in the Mendeleev's periodic table have been removed.
5- There is no confusion regarding the position of isotopes because all the isotopes of an element have the same atomic number.
6- The periodic table is more systematic than the Mendeleev's periodic table and it is easy to remember.
7- In Mendeleev's periodic table transition elements included with other elements, in modern periodic table transition element present in separate block.

Ans 3- The Third alkaline Metal is Calcium(Ca) (2,8,8,2). It has 2 electron in valence shell with valency 2.

Ans 4 -The vertical columns in the periodic table are known as groups while the horizontal rows are known as periods. long form of periodic table has 7 periods and 18 groups

Ans 5- The element name is Sulphur.It is kept in group VI A or group 16 in modern periodic table.
Electronic Configuration= 2,8,6
Number of valence electron in sulphur are 6 present in M shell its valency is 2 as its required 2 electron to complete it octet.

Ans 6- Lithium,Sodium and Potassium all react with water to form alkalis that is lithium hydroxide,Sodium hydroxide, potassium hydroxide,etc. with the liberation of hydrogen gas.
All these metals have one electron in their respective outermost shells.

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