Question

Which equation correctly represents the first electron affinity (ea1) of calcium?

Answer 1

Answer : The correct equation will be:

$Ca(g)+1e^-\rightarrow Ca^-(g)$

Explanation :

Electron affinity : It is defined as the addition of electron to the atom or to the ion. The atom or ion is always in gaseous phase.

In other words we can say that, the gaining of electrons is said to be an electron affinity.

As, the given element is a calcium metal, so it will gain an electron to form a anionic atom.

The balanced and correct equation for first electron affinity of the calcium will be:

$Ca(g)+1e^-\rightarrow Ca^-(g)$

Answer 2

Answer :

The correct answer is : $Ca (g) + e^- \rightarrow Ca^- (g)$

Electron Affinity :

It is defined as energy released  or absorbed when an electrons is added to neutral isolated atom in gaseous state .

The first electron affinity is the energy absorbed or released when one electron is to  outermost  shell of a neutral atom .

The first electron affinity  is generally negative , when electron is added to non metals .  While when electron  is added to metals , the electron affinity is positive.

More the negative electron affinity , more the atom has tendency to accept the electron .

For example :  F(g) + e⁻  → F⁻(g)   ΔH⁰ = - 328.0$\frac{KJ}{mol}$

- 328.0$\frac{KJ}{mol}$  represents  first electron affinity of Fluorine atom .

First electron affinity for Calcium can be written as :

The symbol for Calcium in its ground state is Ca . Since the electron (e⁻) is added so it is written on left  side or reaction . The calcium will accept the electron and will form a negative ion as Ca⁻ .

Hence the equation goes as

$Ca (g) + e^-\rightarrow Ca^- (g)$