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Nuclear Chemistry

Bravo – 15,000 kilotons

Nuclear Chemistry

Radioactive elements

Radioactive elements

Elements with atomic numbers greater than 83 are radioactive Why? These elements have too many protons & neutrons crammed into their nucleus to be stable. What happens? The elements “decay” by giving off mass & energy

Vocabulary Nuclear Reactions – reactions that effect the nucleus of an atom

Radioactive Decay –unstable nuclei lose mass (protons/neutrons) & energy to become stable

178O

Natural transmutation - The nucleus of an atom releases a proton and changes into a different atom. Artificial (man-made) transmutation -The nucleus of an atom is hit with particles that have great quantities of energy. The particles either add to the nucleus or break apart it apart. This changes the atom into a different atom.

Vocabulary

Discovery of Radiation Wilhelm Conrad Roentgen

• discovered X rays https://easyscienceforkids.com/wilhelm-conrad-roentgen-video-for-kids/

Pierre & Marie Curie • Coined “Radioactive” • Nobel Laureates • Discovered several radioactive elements

https://www.biography.com/video/marie-curie-mini-biography-35738691933

Types of Radiation

Radiation

Alpha particles

Beta particles Positron Gamma

particles

• When we are looking at any type of radiation or radioactive decay we must remember that matter is conserved!

Nuclear Symbols

Element symbol

Mass number (p+ + no)

Atomic number (number of p+)

U23592

Alpha Particle Emission Beta Particle Emission

Gamma Ray Emission

Symbol

or

or

Mass

Heavy

Light

No Mass

How it changes

the nucleus

• Decreases the mass

number by 4 • Decreases the

atomic number by 2 • Contains 2 protons

and 2 neutrons

• Converts a neutron into a proton

• Send off a fast moving e- (β)

• Increases atomic number by 1

-High energy radiation –just energy! (gamma rays) -No change to the nucleus -emitted with alpha & beta radiation

Penetration

Low

Medium

High

Protection

provided by…

Paper, clothing

Cardboard, wood

Lead

Danger

Low, slow moving

Medium, fast

High

He42 α4

2 e01− β0

1−γ0

0

Types of Radioactive Decay

alpha production (α, He): helium nucleus

beta production (β, e): gamma ray production (γ):

ThHeU 23490

42

23892 +→

234 234 090 91 1Th Pa e−→ +

γ00

23490

42

23892 2++→ ThHeU

Alpha Radiation

Alpha decay is limited to VERY large, nuclei such as those in heavy metals. (α, He): helium nucleus

Alpha particles in a reaction • Alpha radiation is emitted from U-238

23892U →234

90Th + 42He Is matter conserved? Yes!

• Now you try! • Alpha radiation is emitted from Rn-222 222

86Rn → 21884Po+ 42He

Gamma particles in a reaction

• 23090Th→226

88Ra + 42He + γ – When the alpha particle is released a huge

amount of energy is also released (the gamma particle)!

Beta Radiation

Beta decay converts a neutron into a proton and an e- (β) is released

Beta particles in a reaction • C-14 is a beta emitter, show the decay process • 14

6C →147N + 0-1β

What Happened? • np+; so atomic mass is still 14 • a new p+= atomic number of 7 (now N) • A β-particle flies out of the atom 0

-1 β is the same as 0-1 e

Now you try

40

19K →

4020Ca + 0-1 β

What Happened? np+; so atomic mass is still 40 a new p+= atomic number of 20 (Ca) A β-particle flies out of the atom 0

-1 β is the same as 0-1 e

Positron Particle

• Same mass as an electron • Neutrons can be formed by protons that emit

a positron • They have a negligible mass

– Consequently they are more penetrating than alpha particles

• They have a charge of +1

Positrons in a reaction

• Potassium-38 will emit a positron, show the decay. • 38

19K → 3818Ar + 0+1β

• What Happened? • p+ n; atomic mass is still 38 • p+ n; atomic number decrease by 1; 18 (Ar) • A positron flies out of the nucleus • Now you try • 13

7N → 13

6C + 0+1β

Stop and practice

• Packet page 16-17