# High School Chemistry/Lanthanides and Actinides

To complete our look at the periodic table there is one more group we have to consider. This group holds its own unique position in any pictorial representation of the Periodic Table. The two rows that are generally placed underneath the main Periodic Table are called the lanthanide series and the actinide series. These two rows are produced when electrons are being added to f orbitals. Therefore, this block of elements are referred to as the "f block". The lanthanides are also occasionally referred to the rare earth elements. The f block, as shown in the figure below, are the two rows in yellow.

## Lesson Objectives

* Define the lanthanides and actinides.
* Place the lanthanides and actinides in the periodic table.
* Explain the importance of both the lanthanides and actinides.
* Write electron configurations for lanthanides and actinides.

## Elements Whose Atoms are Filling f Sublevels

There is one group that we have neglected to mention throughout this chapter. This group belongs to a special group found almost disjointed, if you like, from the Periodic Table. They are given the names the Lanthanide Series and the Actinide Series or the lanthanides and the actinides. The lanthanides are an important group of elements. Most of them are formed when uranium and plutonium undergo nuclear reactions. The elements of the lanthanide series are also known as the rare earth elements. Both the lanthanides and the actinides make up what are known as the inner transition series. The f block is given this name because if the f block were placed in its proper numerical position in the Periodic Table, it would be in the transition metals between groups 2 and 3.
The lanthanide series includes elements from number 58 to 71, which is 14 elements. The f sub-level contains seven orbitals and each orbital will hold two electrons. Therefore, it is possible to place 14 electrons in the 4f sub-level.
The lanthanide series fills the 4f sublevel as you move from cerium (Ce) to lutetium (Lu). The same holds for the actinide series that runs from atomic number 90 through to number 103, again 14 elements. Thus, as you move from thorium (Th) at element number 90, you begin to fill up the 5f sublevel and continue to fill up the 5f sublevel until you finish the actinide series at lawrencium (Lr).
| Group → | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
| ↓ Period | | | | | | | | | | | | | | | | | | |
| 1 | 1 H 1.01 | | | | | | | | | | | | | | | | | 2 He 4.00 |
| 2 | 3 Li 6.94 | 4 Be 9.01 | | | | | | | | | | | 5 B 10.1 | 6 C 12.0 | 7 N 14.0 | 8 O 16.0 | 9 F 19.0 | 10 Ne 20.2 |
| 3 | 11 Na 23.0 | 12 Mg 24.3 | | | | | | | | | | | 13 Al 27.0 | 14 Si 28.1 | 15 P 31.0 | 16 S 32.1 | 17 Cl 35.5 | 18 Ar 40.0 |
| 4 | 19 K 39.1 | 20 Ca 40.1 | 21 Sc 45.0 | 22 Ti 47.9 | 23 V 50.9 | 24 Cr 52.0 | 25 Mn 54.9 | 26 Fe 55.9 | 27 Co 58.9 | 28 Ni 58.7 | 29 Cu 63.6 | 30 Zn 65.4 | 31 Ga 69.7 | 32 Ge 72.6 | 33 As 74.9 | 34 Se 79.0 | 35 Br 79.9 | 36 Kr 83.8 |
| 5 | 37 Rb 85.5 | 38 Sr 87.6 | 39 Y 88.9 | 40 Zr 91.2 | 41 Nb 92.9 | 42 Mo 95.9 | 43 Tc 98 | 44 Ru 101 | 45 Rh 103 | 46 Pd 106 | 47 Ag 108 | 48 Cd 112 | 49 In 115 | 50 Sn 119 | 51 Sb 122 | 52 Te 128 | 53 I 127 | 54 Xe 131 |
| 6 | 55 Cs 133 | 56 Ba 137 | 57 La 139 | 72 Hf 179 | 73 Ta 181 | 74 W 184 | 75 Re 186 | 76 Os 190 | 77 Ir 192 | 78 Pt 195 | 79 Au 197 | 80 Hg 201 | 81 Tl 204 | 82 Pb 207 | 83 Bi 209 | 84 Po 209 | 85 At 210 | 86 Rn 222 |
| 7 | 87 Fr 233 | 88 Ra 226 | 89 Ac 227 | 104 Rf 263 | 105 Db 262 | 106 Sg 266 | 107 Bh 264 | 108 Hs 269 | 109 Mt 268 | 110 Ds 272 | 111 Rg 272 | 112 Cn 277 | 113 Nh 284 | 114 Fl 289 | 115 Mc 288 | 116 Lv 292 | 117 Ts 292 | 118 Og 294 |
| Lanthanides | Lanthanides | Lanthanides | Lanthanides | Lanthanides | 58 Ce 140 | 59 Pr 141 | 60 Nd 144 | 61 Pm 145 | 62 Sm 150 | 63 Eu 152 | 64 Gd 157 | 65 Tb 159 | 66 Dy 163 | 67 Ho 165 | 68 Er 167 | 69 Tm 169 | 70 Yb 173 | 71 Lu 175 |
| Actinides | Actinides | Actinides | Actinides | Actinides | 90 Th 232 | 91 Pa 231 | 92 U 238 | 93 Np 237 | 94 Pu 244 | 95 Am 243 | 96 Cm 247 | 97 Bk 247 | 98 Cf 251 | 99 Es 252 | 100 Fm 257 | 101 Md 258 | 102 No 259 | 103 Lr 260 |
| | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. | Alkali metals$^2$Alkaline earth metals$^2$Lanthanides$^{1,}$$^2$Actinides$^2$Transition metals$^2$ Other metalsMetalloidsOther nonmetalsHalogens$^3$Noble gases$^3$ $^1$Natural lanthanides are also known as "rare earths" or "rare-earth elements". $^2$Alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, and poor metals are all collectively known as "Metals". $^3$Halogens and noble gases are also non-metals. |

## Lanthanides and Actinides Vary in Electron Filling Order

The lanthanides and the actinides make up the f block of the Periodic Table. The lanthanides are the elements produced as the 4f sublevel is filled with electrons and the actinides are formed while filling the 5f sublevel. Generally speaking, the lanthanides have electron configurations that follow the Aufbau rule. There are some variations, however, in a few of the lanthanide elements. We will expand a tiny portion of the Periodic Table below to show what happens to some of the electron configurations in the lanthanide and actinide series.
    Lanthanides 58 Ce 140 59 Pr 141 60 Nd 144 61 Pm 145 62 Sm 150 63 Eu 152 64 Gd 157 65 Tb 159 66 Dy 163 67 Ho 165 68 Er 167 69 Tm 169 70 Yb 173 71 Lu 175 Actinides 90 Th 232 91 Pa 231 92 U 238 93 Np 237 94 Pu 244 95 Am 243 96 Cm 247 97 Bk 247 98 Cf 251 99 Es 252 100 Fm 257 101 Md 258 102 No 259 103 Lr 260
Look, for example, at the electron configuration for cerium, the first element of the lanthanide series. Cerium, Ce, is element number 58.
    $_{58}$Ce: 1s$^2$2s$^2$2p$^6$3s$^2$3p$^6$4s$^2$3d$^{10}$4p$^6$5s$^2$4d$^{10}$5p$^6$6s$^2$5d$^1$4f$^1$
or
    $_{58}$Ce: [Xe]6s$^2$5d$^1$4f$^1$
Now look at the electronic configuration for praseodymium, an element used in the making of aircraft engines but also in lighting for making movies. Praseodymium, Pr, is element number 59 and has the following electron configuration.
    $_{59}$Pr: 1s$^2$2s$^2$2p$^6$3s$^2$3p$^6$4s$^2$3d$^{10}$4p$^6$5s$^2$4d$^{10}$5p$^6$6s$^2$4f$^3$
or
    $_{59}$Pr: [Xe]6s$^2$4f$^3$
Notice the d electron is no longer a part of the electron configuration. There are three lanthanide metals that have properties similar to the d block. These are cerium, Ce, lutetium, Lu, and gadolinium, Gd. All of these metals contain a d electron in their electron configuration. The rest, like praseodymium, simply fill the 4f sublevel as the atomic number increases.
Unlike the lanthanide family members, most of the actinide series are radioactive. Most of the elements in the actinide series have the same properties as the d block. Members of the actinide series can lose multiple numbers of electrons to form a variety of different ions. Table 9.14 shows the noble gas electron configuration for the elements of the actinide series.
Table 9.14: Noble Gas Electron Configuration for the Actinide Series :
| Element | Electron Configuration |
| Thorium (Th) | [Rn]7s$^2$6d$^2$ |
| Protactinium (Pa) | [Rn]7s$^2$5f$^2$6d$^1$ |
| Uranium (U) | [Rn]7s$^2$5f$^3$6d$^1$ |
| Neptunium (Np) | [Rn]7s$^2$5f$^4$6d$^1$ |
| Plutonium (Pu) | [Rn]7s$^2$5f$^6$ |
| Americium (Am) | [Rn]7s$^2$5f$^7$ |
| Curium (Cm) | [Rn]7s$^2$5f$^7$6d$^1$ |
| Berkelium (Bk) | [Rn]7s$^2$5f$^9$ |
| Californium (Cf) | [Rn]7s$^2$5f$^{10}$ |
| Einsteinium (Es) | [Rn]7s$^2$5f$^{11}$ |
| Fermium (Fm) | [Rn]7s$^2$5f$^{12}$ |
| Mendelevium (Md) | [Rn]7s$^2$5f$^{13}$ |
| Nobelium (No) | [Rn]7s$^2$5f$^{14}$ |
| Lawrencium (Lr) | [Rn]7s$^2$5f$^{14}$6d$^1$ |

## Lesson Summary

* The lanthanide and actinide series make up the inner transition metals.
* The lanthanide series fill up the 4f sublevel and the actinide series fill up the 5f sublevel.
* The first, middle, and last member of the lanthanide series have properties of the f block and the d block.
* Many of the actinide series have properties of both the d block and the f block elements.

## Review Questions

* Why are the f block elements referred to by some as inner transition elements?
* What do europium and americium have in common as far as their electron configuration?
* What is the electron configuration for Berkelium?
    (a) [Xe]7s$^2$5f$^9$
    (b) [Xe]7s$^2$5f$^9$6'd$^1$
    (c) [Rn]7s$^2$5f$^9$
    (d) [Rn]7s$^2$5f$^9$6d$^1$
* How many f electrons are there in the electron configuration for einsteinium?
    (a) 0
    (b) 11
    (c) 14
    (d) 25
* Write the electron configuration for Ytterbium, Yb.
* What are the valence electrons for Ytterbium, Yb? What periods and sublevels are they in?
* Write the noble gas electronic configuration for uranium, U.
* What are the valence electrons for uranium, U? What periods and sublevels are they in?
* Write the electron configurations for neptunium and then for plutonium. Now write an explanation for what seems to be happening.

## Vocabulary
### actinides

    The elements found in the second period of the f block. These elements fill up the 5f sublevel.

### lanthanides

    The rare earth elements found in the first period of the f block. These elements fill up the 4f sublevel.
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This material was adapted from the original CK-12 book that can be found here. This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License