Question

26. State any four physical properties of metals.
27. Give four points explaining the outline of modern periodic table.
28. Explain the achievements (merits) of Mendeleev's periodic table. in 2 mark
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Answer 1

Answer:

26. Shiny (lustrous) in nature.

Metal is a good conductor of electricity and heat.

Density and melting point is high.

Mouldable (Malleable)

Ductile.

At room temperature, it is in solid form except for mercury.

Opaque.

27. There are 18 vertical columns in the periodic table. Each column is called a group. All elements in a group have similar chemical and physical properties because they have the same number of valence electrons. Periods - In periodic table elements are arranged in a series of rows.

28. Mendeleev's periodic table was one of the greatest achievements in the development of chemistry. ... (B) Correction of atomic masses : The mendeleev's periodic table could predict errors in the atomic masses of certain elements were corrected.

Explanation:

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Answer 2

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26.Metals have many physical properties and some of those are:-

• Metals are lustrous (Shiny).

• Metals are sonorous.

• Metals are malleable (beaten to thin sheets).

• Metals are ductile (drawn into wires).

• Metals are good conductors.

• Metals have high tensile strength.

27.The points that can explain the outline of modern periodic table are :-

• The elements in periodic table are arranged according to their increasing atomic number.

• There are 18 vertical columns called group in a periodic table .

• There are 7 horizontal rows called period in a periodic table .

• The elements in periodic table are divided into metals , non - metals and metalloids.

28. Achievements of Mendeleev's periodic table includes :-

• He arranged the elements on the basis of a specific property(Atomic Mass).

• He left spaces for some elements that were not discovered and even correctly predicted their atomic mass and other properties.

• He corrected the atomic masses of several known elements.