What Is the Reaction That Corresponds to the First Ionization Energy of Potassium, K

Ionization Energy and Electron Analogousness

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The First Ionization Energy

The energy needed to remove one or more than electrons from a neutral cantlet to class a positively charged ion is a physical property that influences the chemical behavior of the atom. By definition, the offset ionization energy of an element is the energy needed to remove the outermost, or highest energy, electron from a neutral atom in the gas phase.

The process by which the beginning ionization free energy of hydrogen is measured would be represented by the following equation.

The magnitude of the first ionization energy of hydrogen can be brought into perspective by comparing it with the free energy given off in a chemical reaction. When nosotros fire natural gas, nigh 800 kJ of energy is released per mole of marsh gas consumed.

The thermite reaction, which is used to weld iron runway, gives off about 850 kJ of energy per mole of atomic number 26 oxide consumed.

The first ionization energy of hydrogen is half again as large as the energy given off in either of these reactions.

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Patterns in the Beginning Ionization Energies

The first ionization energy for helium is slightly less than twice the ionization energy for hydrogen because each electron in helium feels the attractive forcefulness of 2 protons, instead of one.

It takes far less energy, however, to remove an electron from a lithium atom, which has three protons in its nucleus.

This can exist explained by noting that the outermost, or highest energy, electron on a lithium cantlet is in the twosouth orbital. Because the electron in a 2s orbital is already at a higher energy than the electrons in a 1southward orbital, it takes less energy to remove this electron from the atom.

The first ionization energies for the master group elements are given in the two figures below.

Ii trends are apparent from these data.

• In general, the starting time ionization energy increases as we get from left to right across a row of the periodic tabular array.
• The first ionization energy decreases as we go down a column of the periodic table.

The beginning tendency isn't surprising. We might expect the starting time ionization free energy to go larger as we become across a row of the periodic table because the forcefulness of allure between the nucleus and an electron becomes larger equally the number of protons in the nucleus of the cantlet becomes larger.

The second trend results from the fact that the principal breakthrough number of the orbital holding the outermost electron becomes larger as nosotros become down a cavalcade of the periodic table. Although the number of protons in the nucleus also becomes larger, the electrons in smaller shells and subshells tend to screen the outermost electron from some of the force of attraction of the nucleus. Furthermore, the electron being removed when the first ionization energy is measured spends less of its time near the nucleus of the cantlet, and it therefore takes less energy to remove this electron from the cantlet.

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Exceptions to the General Pattern of First Ionization Energies

The figure below shows the first ionization energies for elements in the second row of the periodic table. Although there is a general tendency toward an increase in the kickoff ionization energy as we go from left to correct across this row, there are two small-scale inversions in this blueprint. The first ionization energy of boron is smaller than glucinium, and the first ionization free energy of oxygen is smaller than nitrogen.

These observations tin exist explained by looking at the electron configurations of these elements. The electron removed when a glucinium atom is ionized comes from the 2s orbital, simply a twop electron is removed when boron is ionized.

Exist: [He] 2s ²

B: [He] 2s ² 2p ⁱ

The electrons removed when nitrogen and oxygen are ionized also come from 2p orbitals.

N: [He] 2s ^two 2p ³

O: [He] 2s ² 2p ⁴

Simply there is an important divergence in the manner electrons are distributed in these atoms. Hund'south rules predict that the three electrons in the 2p orbitals of a nitrogen atom all have the same spin, but electrons are paired in one of the 2p orbitals on an oxygen atom.

Hund's rules can be understood by assuming that electrons try to stay equally far apart every bit possible to minimize the force of repulsion between these particles. The 3 electrons in the 2p orbitals on nitrogen therefore enter different orbitals with their spins aligned in the aforementioned direction. In oxygen, two electrons must occupy ane of the 2p orbitals. The strength of repulsion between these electrons is minimized to some extent by pairing the electrons. There is still some balance repulsion between these electrons, however, which makes information technology slightly easier to remove an electron from a neutral oxygen cantlet than we would expect from the number of protons in the nucleus of the cantlet.

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Second, Third, Fourth, and Higher Ionization Energies

By now you know that sodium forms Na⁺ ions, magnesium forms Mgⁱⁱ⁺ ions, and aluminum forms Al³⁺ ions. Simply take you e'er wondered why sodium doesn't form Naⁱⁱ⁺ ions, or even Naⁱⁱⁱ⁺ ions? The answer can be obtained from data for the second, third, and college ionization energies of the element.

The outset ionization free energy of sodium, for example, is the free energy it takes to remove 1 electron from a neutral atom.

Na(g) + free energy Na⁺(thou) + e^-

The 2d ionization energy is the energy information technology takes to remove another electron to grade an Naⁱⁱ⁺ ion in the gas stage.

Na⁺(k) + energy Na²⁺(thou) + e^-

The third ionization energy can be represented past the post-obit equation.

Na²⁺(1000) + energy Naⁱⁱⁱ⁺(k) + due east^-

The energy required to form a Na^three+ ion in the gas phase is the sum of the kickoff, second, and 3rd ionization energies of the element.

Offset, Second, Third, and Fourth Ionization Energies
of Sodium, Magnesium, and Aluminum (kJ/mol)

Information technology doesn't accept much energy to remove 1 electron from a sodium atom to form an Na⁺ ion with a filled-shell electron configuration. Once this is done, nevertheless, it takes near ten times as much energy to pause into this filled-beat configuration to remove a second electron. Because it takes more than energy to remove the 2d electron than is given off in whatever chemic reaction, sodium can react with other elements to course compounds that contain Na⁺ ions simply not Na²⁺ or Na³⁺ ions.

A similar pattern is observed when the ionization energies of magnesium are analyzed. The first ionization energy of magnesium is larger than sodium because magnesium has 1 more proton in its nucleus to concord on to the electrons in the iiisouth orbital.

Mg: [Ne] iiis ²

The second ionization energy of Mg is larger than the first considering it always takes more than energy to remove an electron from a positively charged ion than from a neutral atom. The third ionization energy of magnesium is enormous, however, considering the Mg²⁺ ion has a filled-trounce electron configuration.

The same design can be seen in the ionization energies of aluminum. The first ionization energy of aluminum is smaller than magnesium. The 2d ionization energy of aluminum is larger than the first, and the third ionization free energy is even larger. Although information technology takes a considerable corporeality of energy to remove three electrons from an aluminum atom to form an Alⁱⁱⁱ⁺ ion, the energy needed to pause into the filled-shell configuration of the Alⁱⁱⁱ⁺ ion is astronomical. Thus, it would exist a error to await for an Al^four+ ion as the product of a chemical reaction.

Do Problem 5:

Predict the group in the periodic tabular array in which an element with the following ionization energies would most likely be plant.

1st IE = 786 kJ/mol

2nd IE = 1577

3rd IE = 3232

4th IE = 4355

5th IE = 16,091

6th IE = nineteen,784

Click here to bank check your answer to Exercise Problem 5

Exercise Problem 6:

Utilise the trends in the ionization energies of the elements to explain the post-obit observations.

(a) Elements on the left side of the periodic table are more than likely than those on the correct to class positive ions.

(b) The maximum positive accuse on an ion is equal to the group number of the element

Click here to bank check your answer to Practice Trouble 6

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Electron Analogousness

Ionization energies measure out the trend of a neutral cantlet to resist the loss of electrons. Information technology takes a considerable corporeality of energy, for instance, to remove an electron from a neutral fluorine atom to grade a positively charged ion.

The electron affinity of an chemical element is the free energy given off when a neutral atom in the gas phase gains an actress electron to grade a negatively charged ion. A fluorine atom in the gas stage, for case, gives off energy when it gains an electron to course a fluoride ion.

Electron affinities are more than difficult to measure than ionization energies and are normally known to fewer significant figures. The electron affinities of the principal grouping elements are shown in the figure beneath.

Several patterns can be plant in these data.

• Electron affinities generally become smaller every bit nosotros go down a column of the periodic tabular array for 2 reasons. Get-go, the electron being added to the atom is placed in larger orbitals, where information technology spends less time virtually the nucleus of the atom. Second, the number of electrons on an atom increases as we go down a column, so the force of repulsion between the electron being added and the electrons already present on a neutral atom becomes larger.
• Electron analogousness data are complicated past the fact that the repulsion between the electron being added to the atom and the electrons already present on the cantlet depends on the book of the atom. Amid the nonmetals in Groups VIA and VIIA, this force of repulsion is largest for the very smallest atoms in these columns: oxygen and fluorine. As a event, these elements have a smaller electron affinity than the elements beneath them in these columns as shown in the figure below. From that point on, still, the electron affinities decrease equally we proceed down these columns.

At first glance, there appears to exist no pattern in electron affinity beyond a row of the periodic table, every bit shown in the effigy below.

When these information are listed forth with the electron configurations of these elements, however, they make sense. These data tin be explained by noting that electron affinities are much smaller than ionization energies. Every bit a result, elements such equally helium, beryllium, nitrogen, and neon, which take unusually stable electron configurations, take such small affinities for extra electrons that no energy is given off when a neutral atom of these elements picks up an electron. These configurations are so stable that it actually takes energy to forcefulness 1 of these elements to choice up an actress electron to class a negative ion.

Electron Affinities and Electron Configurations for the First 10 Elements in the Periodic Tabular array

Element		Electron Analogousness (kJ/mol)		Electron Configuration
H		72.8		onedue south 1
He		<0		onesouth 2
Li		59.8		[He] 2s i
Exist		<0		[He] 2s 2
B		27		[He] 2s ii twop 1
C		122.3		[He] 2s ii 2p 2
N		<0		[He] 2s 2 twop 3
O		141.ane		[He] iisouth 2 2p 4
F		328.0		[He] 2south 2 2p v
Ne		<0		[He] iis 2 twop half dozen

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Consequences of the Relative Size of Ionization Energies and Electron Affinities

Students often believe that sodium reacts with chlorine to course Na⁺ and Cl^- ions considering chlorine atoms "like" electrons more than sodium atoms do. At that place is no doubt that sodium reacts vigorously with chlorine to class NaCl.

two Na(s) + Cl_ii(one thousand) 2 NaCl(southward)

Furthermore, the ease with which solutions of NaCl in h2o conduct electricity is evidence for the fact that the production of this reaction is a salt, which contains Na⁺ and Cl^- ions.

NaCl(s)

HiiO

Na+(aq) + Cl-(aq)

The but question is whether it is legitimate to assume that this reaction occurs because chlorine atoms "like" electrons more than sodium atoms.

The first ionization energy for sodium is ane and half times larger than the electron analogousness for chlorine.

Na: 1st IE = 495.8 kJ/mol

Cl: EA = 328.8 kJ/mol

Thus, it takes more energy to remove an electron from a neutral sodium atom than is given off when the electron is picked up by a neutral chlorine atom. We will manifestly have to find another explanation for why sodium reacts with chlorine to grade NaCl. Before we can do this, however, we need to know more most the chemistry of ionic compounds.

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Source: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch7/ie_ea.html

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