Electron affinity refers to the energy released when an electron is added to an empty or partially filled orbital of an isolated gaseous atom in its valence energy level to form an anion with a unit negative charge. This energy release gives electron affinity a negative sign, indicating the attraction of the nucleus for the extra electron. Factors influencing electron affinity include atomic radius, nuclear charge, and the shielding effect of inner electrons. In the periodic table, electron affinities increase from left to right in a period due to the decrease in atomic radius and increase in nuclear charge. Conversely, electron affinities decrease from top to bottom in groups as atomic radii increase with the addition of electronic shells, exerting a shielding effect on the nucleus's attraction towards valence electrons.
What is electron affinity?
Electron affinity is the energy released when an electron adds to an empty or partially filled orbital of an isolated gaseous atom in its valence energy level to form an anion having a unit negative charge. It is a measure of the attraction of the nucleus of an atom for the extra electron.
How is electron affinity influenced by factors such as atomic radius, nuclear charge, and shielding effect of inner electrons?
Electron affinities, like ionization energies, are influenced by factors such as atomic radius, the nuclear charge, and the shielding effect of inner electrons. As the force of attraction between the valence electrons and the nucleus decreases with the increase in atomic radius, electron affinities usually decrease.
How does electron affinity vary in the periodic table?
In a period, electron affinities of elements increase from left to right in the periodic table due to the decrease in atomic radius and increase in nuclear charge. Alkali metals have the lowest electron affinities, while halogens have the highest. In groups, electron affinities usually decrease from top to bottom as atomic radii increase.
What is the significance of the negative sign associated with electron affinity?
The negative sign associated with electron affinity indicates that energy is released when an electron is added to form an anion. This energy release signifies the measure of attraction of the nucleus of an atom for the extra electron.
Can you provide an example of electron affinity values for a specific element?
For example, chlorine (Cl) has an electron affinity of -349 kJ/mol. This negative value indicates the energy released when an electron is added to a chlorine atom to form a chloride ion.
Which factor influences electron affinity along with atomic radius and nuclear charge?
a) Shielding effect of inner electrons
b) Number of protons in the nucleus
c) Atomic mass
d) Number of neutrons
Answer: a) Shielding effect of inner electrons
How is electron affinity represented for chlorine?
a) Cl g + e → Cl- g, H = -349 kJ/mol
b) Cl g + e → Cl+ g, H = +349 kJ/mol
c) Cl- g → Cl g + e, H = -349 kJ/mol
d) Cl+ g → Cl g + e, H = +349 kJ/mol
Answer: a) Cl g + e → Cl- g, H = -349 kJ/mol
What does a negative sign in electron affinity indicate?
a) Energy absorbed
b) Energy released
c) Stable atom
d) Unstable atom
Answer: b) Energy released
Which element has a higher tendency to gain electrons based on electron affinity values?
a) Group I-A elements
b) Group VII-A elements
c) Group II-A elements
d) Group VI-A elements
Answer: b) Group VII-A elements
How is electron affinity related to the attraction of the nucleus for an extra electron?
a) Directly proportional
b) Inversely proportional
c) No relation
d) Equal
Answer: a) Directly proportional