wednesday october 5, 2011 (ionization energy; electron affinity)

WednesdayOctober 5, 2011

(Ionization Energy; Electron Affinity)

We will have a test next Tuesday.

Announcements

Assignment Currently Open

Summative or

Formative

Date Issued

Date Due

Date Into

Grade Book

Last Day

WS – The Electromagnetic Spectrum F 9/23 9/27

WS – Average Atomic Mass F 9/27 9/29

WS – Periodic Properties F 10/3 10/6

TEKSCheck #! F 10/4 10/4

Bell RingerWednesday, 10-5-11

_______________ is the energy required to

remove one electron from a neutral atom

of an element.

Ionization energy

Bell RingerWednesday, 10-5-11

Ionization energy _______ from left to right across a period because of:

increases

Ionization energy ______ from top to bottom down a group because:

electrons removed from atoms of each succeeding element in a group are in higher energy levels, farther

from the nucleus.

decreases

increasing nuclear charge. An increase in the number of protons

more strongly attracts electrons in the same energy level.

Ionization Energy

Ionization energy may be defined as the energy required to remove one electron from a neutral atom of an

element.

This property determines the extent to which an atom is capable of losing electrons in order to

begin the chemical bonding process.

Ionization EnergyIn general, ionization energies of the main-group

elements increase across each period. This increase is caused by increasing nuclear charge. A higher charge more strongly attracts electrons in the same energy

level.Generally

speaking, the energy required for an atom to lose electrons

increases as you move from left to

right across a period.

increases

Ionization EnergyAmong the main-group elements, ionization energies

generally decrease down the groups. Electrons removed from atoms of each succeeding element in a

group are in higher energy levels, farther from the nucleus. Generally

speaking, the energy required to lose electrons get less as you move down a

group. Therefore, they

are removed more easily.

decrease

Bell RingerWednesday, 10-5-11

__________________ is the energy change that

occurs when an electron is acquired by a neutral

atom.

Electron affinity

Bell RingerWednesday, 10-5-11

Electron affinity _______ from left to right across a period because:

increases

Electron affinity _______ from top to bottom down a group because of:

a slight increase in effective nuclear charge down a group, and an increase

in atomic radius down a group.

decreases

adding an electron to an empty sublevel takes less energy than adding electrons to a half-filled

sublevel.

Electron Affinity

Electron affinity is defined as the energy change that occurs when an electron is

acquired by a neutral atom.

Most atoms release energy when they acquire an electron - the quantity of energy released is represented

by a negative number.

Some atoms must be “forced” to gain an electron by the addition of energy - the quantity of energy absorbed is

represented by a positive number.

.

Electron AffinityIn general, as electrons add to the same p sublevel of

atoms with increasing nuclear charge, electron affinities become more negative across each period within the p

block, although there are exceptions.

negativity increases

For example, adding an electron to a

nitrogen atom gives a half-filled p sublevel. This

occurs much more easily than forcing an electron to pair

with another electron in an orbital of the already half-filled p sublevel of a

oxygen atom.

Electron AffinityAs a general rule, electrons add with greater difficulty down a group. This pattern is a result of two competing factors. The

first is a slight increase in effective nuclear charge down a group, which increases electron affinities. The second is an increase in atomic radius down a group, which decreases electron affinities.

In general,the size effect predominates.

decrease

Complete the worksheet entitled “Periodic

Properties.”

Begin the worksheet entitled “The Periodic

Law.”