On the graph of ATOMIC RADIUS vs. ATOMIC NUMBER: A.)There are 5 maxima on this g

Question

On the graph of ATOMIC RADIUS vs. ATOMIC NUMBER:

A.)There are 5 maxima on this graph. List the five elements, (by symbol) whose atomic radii give these maximum values.

Graph of FIRST IONIZATION POTENTIAL vs. ATOMIC NUMBER

B.) Describe your graph. What trends do you see? What is the significance of this?

C.)Generally, the more metallic an element is, the greater the atomic radius and the smaller the first ionization potential. So of all the elements shown on the two graphs, (the Atomic Radii versus Atomic number graph AND on the graph of First Ionization Energy versus Atomic number) what is the element that is most metallic on each of these two graphs? Give the most metallic element on the atomic radii graph first and the most metallic clement on the first ionization energy graph second.

Explanation / Answer

A)

The symbols of most metalic elements of the first group are already given at peak points of the referred graph as,

Li , Na , K , Rb , Cs.

However , for subsequent group (ie group 2) the five elements (which would show peaks , when their atomic radii are plotted against atomic numbers ) are,

Atomic number.................................Symbol...............

........4..................................................Be

........12.................................................Mg

........20................................................Ca

........38................................................Sr

........56...............................................Ba

B )

The first ionization potential ( in eV ) of elements having atomic numbers > 100 are plotted . The following points relating to striking trends in ionization potential (I) is worth noting

1. Maxima with respect to first ionization potential is seen at noble gases which have close electronic shells and a stable electronic configurations.

2. Minima occurs at the alkalie metals ( Li, Na, K,-----) .Their low ionization potentials can be corelated with their high reactivity.

3. Ionization potentials of different elements generally increases as we go across the period.

4 . IP (1) decreases as we move down the group of the periodic table.

The above trend in variation of First Ionization Potential is significant to draw out following conclusions-

(i) The ionization potential depends on two factors ,

.........a) the attraction of electrons towards nucleus

.........b ) the repulsion of electrons from each other.

as a result the effective nuclear charge experienced by valence electron in an atom will be less than the actual charge ( shielding effect ). This situation occurs in the case of alkalie metals which have a lone ns -outermost electron preceded by noble gas configuration.

When we move from lithium to fluorine across the period, successive electrons are added to the orbitals in the same principal quantum level and the shielding of nuclear charge by inner core of electrons does not increase very much to compensate with for increased attraction of electron to the nuleus.Thus across the period , increasing nuclear charge outweighs the shielding. Consequently , the outermost electrons are held more and more tightly and the ionization potential increases across the period.

C )

As inferred out of the two graphs ( 1 . atomic radii vs. atomic numbers & Ionization energy vs. atomic numbers )

it is stated that the atomic radii & ionization potential of elments are closely related properties. Hence the most metallic element is-

Cs (Caesium ) with atomic number 55 ,.......asper graph atomic radius vs. atomic number.

Cs ( Caesium ) with atomic number 55 , .......as per graph ionization poential vs. atomic number.  

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