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Inner Transition Elements

o x i d Bright Lights Yttrium e ( Y 2 O 3 ) a n d e u r o p i u m o x i d e ( E u 2 O 3 ) a r e u s e d i n color television screens to give a bright, natural color red. This blend of lan- thanide elements will give off a red light when it’s hit with a beam of electrons. Other compounds are used to make the additional col- ors required for a natural- looking picture.

There are two series of inner transition elements. The first series, from cerium to lutetium, is called the lanthanides. The lanthanides also are called the rare earths because at one time they were thought to be scarce. The lanthanides are usually found combined with oxygen in Earth’s crust. The second series of elements, from thorium to lawrencium, is called the actinides.

What other name is used to refer to the lanthanides?

The Lanthanides The lanthanides are soft metals that can be cut with a knife. The elements are so similar that they are hard to separate when they occur in the same ore, which they often do. Despite the name rare earth, the lanthanides are not as rare as originally thought. Earth’s crust contains more cerium than lead. Cerium makes up 50 percent of an alloy called misch (MIHSH) metal. Flints in lighters, like the one in Figure 16, are made from misch metal. The other ingredients in flint are lan- thanum, neodymium, and iron.

Figure 16 The flint in this lighter is called misch metal, which is about 50% cerium, 25% lanthanum, 15% neodymium, and 10% other rare earth metals and iron.

The Actinides All the actinides are radioactive. The nuclei of atoms of radioactive elements are unstable and decay to form other elements. Thorium, protactinium, and uranium are the only actinides that now are found naturally on Earth. Uranium is found in Earth’s crust because its half-life is long—4.5 billion years. All other actinides are synthetic elements. Synthetic elements are made in laboratories and nuclear reactors. Figure 17 shows how synthetic elements are made. The synthetic elements have many uses. Plutonium is used as a fuel in nuclear power plants. Americium is used in some home smoke detectors. Californium- 252 is used to kill cancer cells.

What property do all actinides share?

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Ce

Pr

Nd

Pm

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

90

91

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Th

Pa

U

Np

Pu

Am

Cm

Bk

Cf

Es

Fm

Md

No

Lr

Lanthanide Series

Actinide Series

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  • K CHAPTER 4 The Periodic Table

Amanita Pictures

Inner Transition Elements

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