Question

9. Differentiate between the following terms with examples. a. Alkali metals and alkaline earth metals b. Ionization and ionization energy c. Electronegativity and electron affinity

Answer 1

a)

1) Alkali Metal :-

Group-I elements have one electron in their valence shell. They do not occur in the native or free state. These elements are collectively known as alkali metals because their oxides and hydroxides form strong alkalies like NaOH, KOH etc.

Ex. Li, Na, K, Rb, Cs, Fr

2) Alkaline Earth Metal :-

Group-II elements have two electrons in their valence shell. These are commonly called alkaline earth metals because their oxides are alkaline in nature and are found in earth crust.

Ex. Ba, Mg, Ca, Sr, Ba, Ra

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b)

1) Ionization :-

The process by which an atom of element form positive or negative charge species ion by losing or gaining of electrons is called ionization.

Ex.

The atoms of metals (M) lose electrons to form cations.

M + Mn+ + ne

The atoms of non metals (A) accept electrons to form anions.

A +ne + A-

(Where n = number of electrons transferred)

2) Ionization Energy :-

The amount of energy required to remove most loosely bound electron from an isolated gaseous atoms of element to form positive gaseous ion in its ground state is called ionization energy.

Ex.
A(g) +IE+At+e

for second ionization energy
A +IE + A+e

since, Third ionization energy will be higher than the second and so on.

i.e IE₃ > IE₂ > IE₁

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c)

1) Electronegativity :-

The tendency of an atom to attract the shared electron pair towards itself in a covalent bond.

In a periods as we move from left to right electronegativity increases, while in the groups electronegativity decreases down the group.

Electronegativity order of some elements (on Pauling scale) is

F (4.0) > O (3.5) > N (3.0) = Cl (3.0) > Br (2.8)

2) Electron affinity :-

The amount of energy released when an electron is added in an isolated gaseous atom is called electron affinity.

Ex.
$9) + + Io + energy