Nuclear chemistry
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Nuclear Chemistry. “ regular ” chemistry involves only the ELECTRONS in atoms. All the rest of this year we will be studying only “regular” chemistry. “ nuclear ” chemistry involves only the NUCLEUS in atoms. In this chapter (and only this chapter) we will be studying “nuclear” chemistry.

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Nuclear Chemistry

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Nuclear chemistry

Nuclear Chemistry


Nuclear chemistry

“regular” chemistry involves only the ELECTRONS in atoms

All the rest of this year we will be studying

only “regular” chemistry


Nuclear chemistry

“nuclear” chemistry involves only the NUCLEUS in atoms

In this chapter (and only this chapter) we will be studying

“nuclear” chemistry


Important reminder

Important Reminder!

  • Every atom of the same element must have the same number of PROTONS in its nucleus

  • For example, for Lithium to be Lithium, it must have 3 protons. An element with only two protons would be He, with 4 protons Be

  • If the number of protons in a nucleus changes, the atom becomes a different element!


Remember the alchemists

Remember the alchemists?

  • They wanted to change Pb (82 protons) into Au (79 protons)

  • To achieve this would have meant removing 3 protons from the Pb atom’s nucleus

  • Alchemists would have needed to do NUCLEAR chemistry


Stability of atoms

Stability of atoms

  • All the atoms we have studied so far have been “stable”. That means they stay the same and don’t change into other atoms

  • Some atoms are notstable. They tend to “decay” into other atoms.

  • Unstable atoms are called RADIOISOPTOPES


Which atoms are unstable

Which atoms are unstable?

  • The ratio of protons and neutrons in the nucleus determines an atom stability

Stable

atoms

# of n = # of p

(1 to 1 ratio)

All atoms with more than

83 protons are unstable


Which atoms are unstable1

Which atoms are unstable?

  • All atoms with more than 83 protons

  • Some isotopes of atoms with less than 83 protons do not have the right proton to neutron ratio to be stable

    Remember! An isotope is an atom with more or less neutrons than other atoms of that same element


What happens when an unstable atom decays

What happens when an unstable atom “decays” ?

  • It emits (gives off) radiation particles.

    This means it is radioactive.

  • It makes a new atom that is more stable


Types of radiation particles

Types of Radiation particles

  • Alpha

  • Beta

  • Positron

  • Gamma Ray


Alpha particles

Alpha Particles

αGreek letter alpha

It is the nucleus of a He atom (no e-)

with 2 protons, 2 neutrons and

a charge of +2

He

4

2


Beta particles

Beta Particles

-

β or βGreek letter beta

Like an electron except it comes

out of the nucleus, not the e- cloud

has negligible (no) mass

has a charge of -1


Positron particles

Positron Particles

+

βGreek letter beta

has negligible (no) mass

has a charge of +1

Like an e- (or β) but with a

positive charge


Gamma rays

Gamma Rays

γ Greek letter gamma

High energy particle, like x-rays

no mass

no charge


Penetrating power

Penetrating power


When an unstable atom undergoes alpha decay

When an unstable atom undergoes alpha decay…..

radiation

Parent atom

Daughter product

+ He

Th

U

4

2

231

90

235

92

decays to

Thorium-231 and an alpha particle

Uranium-235


What is happening here

What is happening here?

+ He

At

Fr

4

2

216

85

220

87


What is happening here1

What is happening here?

+ He

At

Fr

4

2

216

85

220

87

Fr-220 decays to At-216 and an alpha particle


The following unstable atoms decay by emitting an alpha particle

Ra -226

Rn- 222

Th-232

Look in Table N to find other atoms whose decay mode is also an alpha particle

The following unstable atoms decay by emitting an alpha particle


Write the decay equation for

Write the decay equation for:

Ra -226

Step 1: Re-write the atom symbol so it includes both atomic mass and atomic number (look it up!)

Ra

226

88

Atomic mass

Atomic number


Write the decay equation for ra 226

Write the decay equation for Ra-226:

Step 2: Put the unstable atom on the left side of the decay arrow

Ra

226

88

Radium -226 decays to


Write the decay equation for ra 2261

Write the decay equation for Ra-226:

Step 3: Look up decay mode for the atom in Table N and write that after the decay arrow

α

Ra

226

88

4

2

Radium -226 decays to alpha

particle


Write the decay equation for ra 2262

Write the decay equation for Ra-226:

Step 4: Find the daughter product by conserving mass and charge

226 = 4 + 222

α

Ra

X

226

88

4

2

222

86

+

88 = 2 + 86

Radium -226 decays to alpha and atom X

particle


Write the decay equation for ra 2263

Write the decay equation for Ra-226:

Step 5: Identify the daughter product by looking up its atomic number in the periodic table

α

Ra

Rn

226

88

4

2

222

86

+

Radium -226 decays to alpha and Radon-222

particle


You try it for

You try it for:

Radon -222

Thorium – 232

Uranium - 233


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