Question

Explain the observed values 496kg/mole and 373kg/mol of the first ionization enthalpies of Na and Mg respectively.


please help me ​

Answer 1

Answer:

Explanation:

CHEMISTRY

The first ionization enthalpy (Δ

t

​

H) values of the third period elements, Na, Mg and Si are respectively 496, 737 and 786 kJ mol

−1

. Predict whether the first Δ

t

​

H value for Al will be more close to 575 or 760 kJ mol

- 1

? Justify your answer.

December 27, 2019avatar

Anushka Monika

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ANSWER

The electronic configuration are as follows;

1

​

1Na(3s)

1

,

1

​

2Mg(3s)

2

,

1

​

3Al(3s)

2

(3p)

1

,

1

​

4Si(3s)

2

(3p)

2

The ionisation energy of Mg will be larger than that of Na due to fully filled configuration (3s)

2

The ionization of Al will be smaller than that of Mg due to one electron extra than stable configuration but smaller than Si due to increase in effective nuclear charge of Si.

$$Na<Mg>Al<Si$$

So, the first Δ

t

​

H value of Al will be more close to 575 Kj/mol. The value for Al should be lower than that of Mg because of effective shielding of 3p electron from the nucleus by 3s electron