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Thursday, June 18, 2020

What is atomic density ? give the periodicity of atomic density in periods and groups.

Atomic Density:

Density is the ratio of mass and volume. Higher the atomic volume leads to lower density as vice versa lower the atomic volume leads to higher density.

(A) Trends in group:

When we move top to bottom in a group the atomic density generally increases, it is due to increasing in atomic volume and atomic mass because top to bottom in group, number of shells increases but mass is more and more increases with respect to volume, so finally the atomic density in a group increases.

(B) Trends in period: 

When we move from left to right along with a period, the atomic density increases and become maximum at mid period , and after that decrease.

(C) Atomic density depends upon two factors these are given as.

(i) The electronic configuration of inner most shells

(ii) Packing capacity 

Exception:

(1) Density of Na > Density of K

Reason: 

The density of 'Na' is greater than the density of 'K' .It is due to the inner shells of 'Na' atom is fully filled but the shells the inner most shells of 'K' not full filled.

11Na= 1s2 2s2 2p6 3s1 (Completely filled Inner shell s)

19K= 1s2 2s2 2p6 3s1 3p6 3d0, 4s1 (incomplete inner shells)

(2) Density of Mg > Density of Ca 

Reason:

The density of 'Mg' is greater than the density of of 'Ca' .It is due to the inner shells of 'Mg' atom is fully filled but the shells the inner most shells of 'Ca' not full filled.

12Mg= 1s2 2s2 2p6 3s2(Completely filled Inner shell s)

20Ca= 1s2 2s2 2p6 3s1 3p6 3d0, 4s2 (incomplete inner shells)

Related Questions:

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(2) Name of total metalloids present in periodic table ?

(3) Total numbers of elements which are liquid at normal temperature is ?

(4) What is Mendeleev's periodic table ? give important features and draw back of Mendeleev's table.

(5) What is atomic volume ? and what is periodicity of atomic volume in groups and periods ?

(6) Why there are 2, 8 and 8 elements in first, second and third periodic of periods table respectively ? Explain.

(7) In alkali metal group which is the strongest reducing agent in aqueous solution and why?

(8) The electron affinity of sulphur is greater than oxygen. Why?

(9) The first ionization energy of carbon atom is greater than that of boron atom, whereas reverse is true for the second ionization energy. Explain.

(10) The electronegativities of B, Al, Ga are 2.0, 1.5, 1.6 respectively. The trend is not regular. Explain.

(11) Li2CO3 decomposes on heating but other alkali metal carbonates don’t. Explain.

(12) Of all noble metals, gold has got a relatively high electron affinity. Explain.

(13) Ionization energy of Boron is smaller than Beryllium even though effective nuclear charge is higher?

(14) What are the increasing order of ioni radii of first group elements in water ?

(15) What are the increasing order of molar conductivity of first group elements in water ?

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