7 (a) Explain what is moart by the atomic radius of an element (b) The atomic ra

Question

7 (a) Explain what is moart by the atomic radius of an element (b) The atomic radii of the elements are found in Table 9 of the B data booklet why no values for ionic radi are given for the noble gases (il) Describe and explain the trend in atomic radii across the Period 3 elements 8 Si has an ionic radius of 4.2 x 10 m and has an ionic radusof27.10 Esplainthelage difference in size between the Sr and S iors 9 Which of the following is a property of gaseous atome? ionization energy D L and Il ll electron affinity C and lll electronegativity

Explanation / Answer

(7)

(a) Atomic radius: The mean distance from the center of the nucleus to the boundary of the surrounding electron cloud.

(b)

(i) Because gases do not form compounds (i.e ions) as they are already in more stable state.

(ii)Going across a period,

* The number of protons in the nucleus increase, so the nuclear charge increases

* There are more electrons, but the increase in shielding is negligible because each extra electronenters the same principal energy level.

* Therefore the force of attraction between the nucleus and the elecrons increases

* So, the atomic raidus decreases in a period from left to right.

(8) For an element its positive ion has less size and negative ion has more size than the atomic size.

This is becuase of same number of protons attract less number of electrons in positive ion but more number of electrons in anion.

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