Why the value of second electron affinity is positive whereas first electron affinity is always negative?

Why the value of second electron affinity is positive whereas first electron affinity is always negative?

When an neutral atom takes electron it gives out energy so first electron affinity is negative. But when we try to add an electron in a uni negative ion it repels the coming electron due to more no of electrons than protons, thus second electron affinity is always negative.

Why the second electron affinity value of oxygen is positive?

The second electron affinity of oxygen is positive because after adding two electrons to its neutral oxygen atom, it attains a noble gas configuration. A noble gas configuration being most stable, releases energy to decrease the total energy of the configuration.

Why are electron affinity values positive?

Unlike ionization energies, which are always positive for a neutral atom because energy is required to remove an electron, electron affinities can be negative (energy is released when an electron is added), positive (energy must be added to the system to produce an anion), or zero (the process is energetically neutral) …

Why can electron affinity be positive or negative?

Electron affinities are negative numbers because energy is released. The elements of the halogen group (Group 17) gain electrons most readily, as can be seen from their large negative electron affinities. This means that more energy is released in the formation of a halide ion than for the anions of any other elements.

Why second electron affinity of an element is always endothermic?

2nd electron affinity is always endothermic (positive) because the electron is added to an ion which is already negative therefore it must overcome the repulsion.

Why can’t we measure the second electron affinity for an atom?

It is difficult to add a second electron primarily because of the increased electron-electron repulsion that occurs with the second electron.

Why is 2nd electron affinity endothermic?

Why is the second electron affinity of oxygen negative explain?

There is energy released in bringing in the negative electron up to the positive nucleus. Because the electron is negatively charged you can see that there will be repulsion between the ion and the electron making the process endothermic, hence the positive value.

What does positive electron affinity mean?

The electron affinity is defined as the energy change that occurs when an atom gains an electron, releasing energy in the process. If a reaction is exothermic, the change in energy is negative. This means that the electron affinity is positive.

Which element has the most positive electron affinity?

Therefore, chlorine has a higher electron affinity than fluorine, and this orbital structure causes it to have the highest electron affinity of all of the elements.

Is the electron affinity of be negative?

Notice the sign on the energy is negative. This is because energy is usually released in this process, as opposed to ionization energy, which requires energy. A more negative electron affinity corresponds to a greater attraction for an electron….Electron Affinity Trends.

Element	Electron Affinity
Cl	-348.7 kJ/mole
F*	-327.8 kJ/mole

Why is the second electron affinity negative?

How is the second affinity of an electron defined?

Defining second electron affinity. The second electron affinity is the energy required to add an electron to each ion in 1 mole of gaseous 1- ions to produce 1 mole of gaseous 2- ions. This is more easily seen in symbol terms.

What does it mean when an atom has a positive affinity?

Having a positive affinity means the atom has a increased attraction to an electron. The reason electron affinity increases across a period is due to the increase in stability of the electron configuration (lower energy state). Negative affinity means an atom does not want to gain an electron because it’s electron configuration is already stable.

What is the energy released in the first electron affinity?

Defining first electron affinity The first electron affinity is the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions. This is more easily seen in symbol terms. It is the energy released (per mole of X) when this change happens.

Why is it difficult to add a second electron?

It is difficult to add a second electron primarily because of the increased electron-electron repulsion that occurs with the second electron. Since adding the first electron is exothermic, while adding the second electron is endothermic, the sign reverses when we measure the energy added or released by these two processes.