Question

a). explain characteristics and limitations of Dobereiner's triads

b). what is metallic and non metallic character?​

Answer 1

✪ Characteristics of Dobereiner's triads :

• ➮ Properties of elements in each triad were similar.

• ➮ Dobereiner showed that when three elements in a triad were written in the order of their increasing atomic masses.

• ➮ The atomic mass of the middle element was roughly the average of the atomic masses of the other two elements.

★ Limitation of Dobereiner's triads :

• ➣ Dobereiner could identify only three triads.

• ➣ He was not able to prepare triads of all the known elements.

⌬ Metallic and non-metallic character :

• » Metallic character means the tendency of an atom to lose electrons.

• » Metallic character decreases across a period as the effective nuclear charge increases.

• » Metals are electro-positive as they tend to lose electrons while forming bonds.

• » Metallic character increases as we go down a group as the effective nuclear charge decreases.

• » Non-metals are electro-negative.

• » They tend to form bonds by gaining electrons.

• » Metals are found on the left side of the periodic table while non-metals are towards the right hand side of the periodic table.

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Answer 2

He failed to arrange all the elements in triads having same chemical properties.