6 a. Na has largest atomic radious. Explanation: Across a period, atomic radius

Question

6 a. Na has largest atomic radious.

Explanation: Across a period, atomic radius decreases from left to right within a period due to the  increase in number of protons and electrons. On the other hand down a group, atomic radius increases because due to the increasing quantum number (n), the valence electrons are further away from the nucleus . Electron shielding prevents the outer electrons from being attracted to the nucleuswhich result in increase in atomic radius .

If we look at position of elements in peridic table then atomic radoius increases in the following order

O < P < Mg < Na

6. b ) Oxygen (O) has most negative electron attachment enthalpy.

The electron attachment enthalpy, HEA, is the energy that is given out when a neutral atom in the gas phase combines with a free electron. If this value is positive, then energy is required to attach the electron, resist anion formation.

Now, electron affinity generally decreases down a group of elements &  increases from left to right within a period.

So, the order increasing electron affinity will be

Na < Mg < P < O

6 c)  Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase.

Now, ionization energy of the elements within a period generally increases from left to right due to valence shell stability & within a group generally decreases from top to bottom due to electron shielding.

So, the order of increasing ionization energy will be

Na < Mg < P < O

Answer 7.

The electronic configuration of this element is 1s22s22p63s23p64s2

This element is Ca having atomic number 20 & it is an alkaline earth metal

Number of s electrons are 8

Number of p electrons are 12

Number of d electrons is zero

Explanation / Answer

(d) Ne

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