Ionization Energies Mike Jones Pisgah High School Canton NC Originated 11/20/11 Last revision 05/19/12

Ionization energy The energy needed to remove an electron completely from at atom. Depends upon …. The attraction between the positively charged nucleus and the negatively charged electron. The repulsion between the negatively charged electrons.

Ionization energy The energy needed to remove an electron completely from at atom. Coulomb’s Law the effective nuclear charge As applied to the atom a constant the charge of the electron kq1q2 F = Force of attraction r2 the distance between the nucleus and the electron Some of the attraction of the outermost electron to the nucleus is reduced because of repulsion between the outermost electron and the remaining electrons. The apparent charge on the nucleus is called the effective nuclear charge, Zeff.

The ionization energy is high when there is a strong force of attraction between the nucleus and the outermost electrons. With a low ionization energy, there is less attraction between the nucleus and the electron.

Helium has a very large ion ionization energy, which indicates a very strong attraction between the nucleus and the electron. That electron is at a lower energy, and a large amount of energy is needed to remove the electron. The ionization energy of lithium is very low, which indicates a weak attraction. That electron is already at a higher energy and little additional energy is needed to remove the electron.

Ionization energy is a periodic property. The peaks are the inert gases. The valleys are the alkali metals. See how the pattern repeats for each period

The ionization energy generally increases along a period as the atomic number increases and the charge on the nucleus increases. This produces more attraction between the nucleus and the electron, resulting in more energy being needed to remove the electron.

The ionization energy increases very little for the first row of the transition metals despite an increase in the number of protons. The effective nuclear charge of the transition metals increases only marginally, and the sizes of the atoms remain close to the same.

+

+ 2

+ 2

+ 2

+ 2

+ 2

+ 2

+ 2

+ 2

+ 2 8

+ 2 8

+ 2 8

+ 2 8

+ 2 8

+ 2 8

+ 2 8

+ 2 8

+ 2 8 8

+ 2 8 8

+ 2 8 8 18

+ 2 8 8 18

+ 2 8 8 18 18

+ 2 8 8 18 18

2 + 8 8 18 18 32 2 8 8 18 18

Q. Eight electrons are filling the second energy level. Why does the ionization energy increase along a period? A. The number of protons is increasing and Zeff increases.

Why are there “blips” in the ionization energies?

One hypothesis is that there are two energy sublevels, very close together, making up the second energy level.. Going from Be to B, goes from one sublevel to the other and less additional energy is needed to remove an electron from the sublevel with the greater energy.

Electrons in the higher sublevel One hypothesis is that there are two energy sublevels, very close together, making up the second energy level.. Going from Be to B, goes from one sublevel to the other and less additional energy is needed to remove an electron from the sublevel with the greater energy. Electrons in the lower sublevel

Electrons in the higher sublevel The same is true for the third energy level. Electrons in the lower sublevel

There are many limitations of the Bohr model, including the fact that the calculations work only for hydrogen. But there is one overriding reason why the Bohr model is so important to our study of the atom and the arrangement of electrons. The Bohr model tells us that electrons are located only in certain, discrete energy levels and that they can only change from one energy level to another by gaining or losing energy.

The “excited electron” is located in one of these energy levels The Bohr model of hydrogen. There are only a few discrete energy levels. 4 The “excited electron” is located in one of these energy levels 3 2 The ground-state electron is located in the lowest energy level. 1

The Quantum mechanical model deals with mulit-electrons atoms with many more energy levels. 1 2 8 3 18 4 32 5 50 The number of electrons in the nth energy level is given by 2n2. The Bohr model showed only 8 electrons in the third energy level. Where are the other ten electrons?

The Quantum mechanical model has more energy levels available to electrons n is the “principal quantum number, one of 4 numbers that uniquiely describe each electron in an atom 4 n 2n2 1 2 8 3 18 4 32 5 50 3 Except for the first energy level, each energy level in the Bohr model is “subdivided” into two or more “sublevels.” 2 1

In multi-electron atoms the original Bohr energy levels are split into sublevels. 4 n 2n2 1 2 8 3 18 4 32 5 50 3 2 1

In multi-electron atoms the original Bohr energy levels are split into sublevels. 4 n 2n2 1 2 8 3 18 4 32 5 50 3 2 1

Overlap between energy sublevels. In multi-electron atoms the original Bohr energy levels are split into sublevels. 4 Overlap between energy sublevels. n 2n2 1 2 8 3 18 4 32 5 50 3 2 1

The letters s, p, d and f are used to label the sublevels. In multi-electron atoms the original Bohr energy levels are split into sublevels. The letters s, p, d and f are used to label the sublevels. 4f 4d 4 4p n 2n2 1 2 8 3 18 4 32 5 50 3d 4s 3 3p 3s s = sharp p = principal d = diffused f = fundamental 2p 2 2s 1 1s

The letters s, p, d and f are used to label the sublevels. In multi-electron atoms the original Bohr energy levels are split into sublevels. The letters s, p, d and f are used to label the sublevels. 4f 4d 4 32 4p n 2n2 1 2 8 3 18 4 32 5 50 3d 4s 3 3p 18 sublevel number of electrons s 2 p 6 d 10 f 14 3s 2p 2 8 2s 2 1 1s

s p d f 2 6 10 14 Periodic table - Sublevels How many electrons go in each region? 14

Since we can’t see atoms or the electrons we have know idea what they actually look like. Yet we need a way to represent the organization of electrons in an atom. Much like technicians use a schematic diagram to represent the components in an electronic circuit, chemists use the electron energy diagram to represent electrons in an atom.

Much like technicians use a schematic diagram to represent the components in an electronic circuit, chemists use the electron energy diagram to represent electrons in an atom.

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p 6s 4f 5d 6p 7s 5f 6d 7p E n e r g y Electron Energy Diagram The electron energy diagram is a “schematic diagram” of an atom, representing the arrangement of electrons. It consists of numbers, letters and lines denoting the orbitals in the various energy sublevels. n 2n2 1 2 8 3 18 4 32 5 50 s 2 p 6 d 10 f 14

The number is the principal quantum number, n. 3d 4d 5s 5p 6s 4f 5d 6p 7s 5f 6d 7p E n e r g y Electron Energy Diagram Each of the lines represents an “orbital” where up to two electrons can be located. The number is the principal quantum number, n. n 2n2 1 2 8 3 18 4 32 5 50 s 2 p 6 d 10 f 14

An orbital is a “region in space” within an atom where up to two electrons can be located. An s-orbital is spherical. Two electrons. The p-orbitals are “dumbell” shaped. Each orbital contains two electrons, for a total of six The Shrodinger wave equation predicts the shape of the orbitals.

The five d-orbitals are shaped like this The five d-orbitals are shaped like this. Each orbital can contain two electrons, for a total of 10 electrons. The transition metals are filling the d-orbitals.

An orbital in the energy diagram is represented by a horizontal line An orbital in the energy diagram is represented by a horizontal line. On the line we place two arrows, one pointing up and one point down, to represent the two electrons in the orbital. Orbital Orbital with one electron Orbital with two electrons Electrons, have the same charge and repel each other. How can two electrons coexist in an orbital where they are fairly close together? Electrons, have a property called spin, which has nothing to do with the electrons spinning. Spin is a magnetic property. Each electron acts like a tiny magnet. Orienting the electrons with opposite spin allows the electrons to occupy the same orbital.

Electron Energy Diagram for Arsenic 2p 3s 4s 3p 4p 3d 4d 5s 5p Each horizontal line represents an orbital, a region which can be occupied by up to two electrons. E n e r g y Electrons with opposite spin are represented by up and down arrows. The electron energy diagram represents the arrangement of the electrons in their respective energy levels and sublevels.

Electron Energy Diagram for Arsenic Hund’s rule says that orbitals at the same energy each get one electron before the second electron is added to an orbital. 1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p E n e r g y Hund’s rule also says that all the electrons in the singly occupied orbitals will have the same spin. This is why all the arrows in the 4p are in different orbitals and pointed up.

Electron Energy Diagram 7p Electron Energy Diagram 6d 5f 7s 6p 5d 4f 6s E n e r g y 5p 4d 5s 4p 3d 4s 3p 3s 2p 2s 1s

Electron Energy Diagram 1s

Electron Energy Diagram The second energy splits into two sublevels called “s” and “p”. An s-sublevel holds two electons. A p-sublevel holds up to six electrons in three orbitals. 2p 2s 1s

Electron Energy Diagram The third energy splits into three sublevels, the “s”, the “p”, and the “d”. The d-sublevel holds up to ten electrons in five orbitals. E n e r g y 3d 3p 3s 2p 2s 1s

Electron Energy Diagram Notice that the 4s sublevel is lower in energy than the 3d sublevel. 4f E n e r g y The fourth energy splits into four sublevels, the “s”, the “p”, the “d”, and the “f ”. The f-sublevel holds up to 14 electrons in seven orbitals. 4d 4p 3d 4s 3p 3s 2p 2s 1s

Electron Energy Diagram 5f 5d 4f E n e r g y 5p Notice the overlap again in the 5s and 4d, and the location of the 4f sublevel. 4d 5s 4p 3d 4s 3p 3s 2p 2s 1s

Electron Energy Diagram 5f 6p 5d 4f 6s E n e r g y 5p The 6s-sublevel is lower in energy than the 4f sublevel. 4d 5s 4p 3d 4s 3p 3s 2p 2s 1s

Electron Energy Diagram 7p Electron Energy Diagram 6d 5f 7s The 7s-sublevel is lower in energy than the 5f sublevel. 6p 5d 4f 6s E n e r g y 5p 4d 5s 4p The energy sublevels are filled in order from lowest energy to highest energy. 3d 4s 3p 3s 2p 2s 1s

Electron Energy Diagram 1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p 6s 4f 5d 6p 7s 5f 6d 7p E n e r g y Electron Energy Diagram The order in which the energy sublevels are filled follows the red line. This is called the Aufbau principle. Aufbau means “building up”, and refers to the building up of the atom one electron at a time.

Periodic table - Sublevels f

Order in which the energy sublevels are filled.

Electron Energy Diagram 7p Electron Energy Diagram 6d 5f 7s 6p 5d 4f 6s E n e r g y 5p 4d The order in which the orbitals are filled can also be predicted from the graph of ionization energy. 5s 4p 3d 4s 3p 3s 2p 2s 1s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p H 1s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p He 1s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Li 1s 2s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Be 1s 2s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p B 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p C 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p N 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p O 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p F 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ne 1s 2s 2p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Na 1s 2s 2p 3s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Mg 1s 2s 2p 3s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Al 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Si 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p P 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p S 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Cl 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ar 1s 2s 2p 3s 3p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p K 1s 2s 2p 3s 3p 4s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ca 1s 2s 2p 3s 3p 4s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Sc 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ti 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p V 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Cr 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Mn 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Fe 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Co 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ni 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Cu 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Zn 1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ga 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Ge 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p As 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Se 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Br 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Kr 1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Rb 1s 2s 2p 3s 3p 4s 3d 4p 5s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Sr 1s 2s 2p 3s 3p 4s 3d 4p 5s

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Y 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Tc 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Cd 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p In 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Sb 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Xe 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p Cs 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

Electron Energy Diagram for Arsenic 2p 3s 4s 3p 4p 3d 4d 5s 5p We can represent the arrangement of electrons more simply by using the “electron configuration.” E n e r g y 1s2, 2s2 2p6, 3s2 3p6, 4s2, 3d10, 4p3

Electron Energy Diagram for Arsenic 2p 3s 4s 3p 4p 3d 4d 5s 5p We can simplify the “electron configuration” even more by using the “inert gas core” to represent the electrons which do not take part in chemical reactions. E n e r g y 1s2, 2s2 2p6, 3s2 3p6, 4s2, 3d10, 4p3 Inert gas core – the inert gas is argon.

Electron Energy Diagram for Arsenic 2p 3s 4s 3p 4p 3d 4d 5s 5p We can simplify the “electron configuration” even more by using the “inert gas core” to represent the electrons which do not take part in chemical reactions. E n e r g y Write the symbol of the inert gas in square brackets. 1s2, 2s2 2p6, 3s2 3p6, 4s2, 3d10, 4p3 Ar

Electron Energy Diagram for Arsenic Write the electron configuration using the inert gas core for the following elements: 1s 2s 2p 3s 4s 3p 4p 3d 4d 5s 5p E n e r g y 1. Al 4. P 2. V 5. Sn 3. Br 6. Bi 1s2, 2s2 2p6, 3s2 3p6, 4s2, 3d10, 4p3 Ar

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 Write the electron configuration using the inert gas core for the following elements: [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 Valence electrons are the outer-most electrons which are involved in bonding. How many valence electrons does each element have?

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 1. Al 3 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 Some transition metals have their valence electrons in the s and d orbitals.

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 3. Br 7

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 3. Br 7 4. P 5

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 3. Br 7 4. P 5 5. Sn 4

1. Al 4. P 2. V 5. Sn 3. Br 6. Bi [Ne] 3s2 3p1 [Ar] 4s2, 3d3 The valence electrons have the highest principal quantum number. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 3. Br 7 4. P 5 5. Sn 4 6. Bi 5

[Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 The valence electrons have the highest principal quantum number. Look at the Roman numeral at the top of the column for each element. Look at the Roman numeral at the top of the column for each element. [Ne] 3s2 3p1 [Ar] 4s2, 3d3 [Ar] 4s2, 3d10, 4p5 [Ne] 3s2, 3p3 [Kr] 5s2, 4d10, 5p2 6. [Xe] 6s2, 4f14, 5d10, 6p3 1. Al 3 2. V 5 3. Br 7 4. P 5 5. Sn 4 6. Bi 5

The Roman numeral at the top of each column on the period table tells the number of valence electrons. 1. Al 3 2. V 5 3. Br 7 4. P 5 5. Sn 4 6. Bi 5

Mike Jones Pisgah High School Canton NC 28716 mjones@haywood.k12.nc.us

Spare parts E n e r g y 7p 6d 5f 7s 6p 5d 4f 6s 5p 4d 5s 4p 3d 4s 3p + 4d 5s 4p 3d 4s 3p 3s 2p 2s 1s