What are the trends for electron affinity?
Down a group, the electron affinity decreases. Across a period, the electron affinity increases.
Remember : electron affinity is the energy released by a gaseous atom when it gains an e- in its outermost shell. Simply, it is the atom's attraction to electrons.
Down a group. The electron affinity decreases. • The number of energy levels increases as we go down a group. As such, e- get farther and farther away from the nucleus. Elements farther down a group, therefore, do not attract other e- as strongly than elements further up a group. • The increased nuclear shielding (due to the increasingly number of filled, inner e- shells that protect the outer e- from the pull of the nucleus) decreases the attraction for new electrons. • Although the nuclear charge (i.e. the # of p+) increases down a group, increasing the pull from the nucleus on outer e-, the increased nuclear shielding reduces the pull of the nucleus.
Across a period The electron affinity increases. • From L to R, the number of energy levels stays the same. The electron configuration gets closer to a stable octet (more energy is released once atoms obtain their stable octet). • Nuclear shielding stays the same. • The nuclear charge increases and e- are held more closely to the nucleus. Therefore, they attract e- more strongly.
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The trends for electron affinity generally follow these patterns:
- Electron affinity increases across a period from left to right.
- Electron affinity decreases down a group from top to bottom.
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When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.
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