NUCLEAR CHANGE

1. NUCLEAR CHANGE

2. Nuclear Change Nuclear change: • Definition: when an unstablenucleus spontaneously changes to form a more stable nucleus • Involves the release of particles, electromagnetic waves or both • This process is called: RADIOACTIVITY!

3. Nuclear Change • Types of radiation: • Beta particle (β particle) – charged electron emitted during a certain type of radio active decay, known as beta decay • Beta Decay stabilizes nuclei by converting neutrons to protons • In Beta decay, a neutron emits a high-energy electron (a beta particle) and changes into a proton! n p + e- Important Point!

4. Nuclear Change If an element adds a proton to its nucleus by Beta decay, then we must have……

5. Nuclear Change Formula for beta decay: 10n 1+1p + 0-1e For example, carbon-14 can beta decay to Nitrogen 14 146C 147N + 0-1e

6. Nuclear Change Result of Beta Decay: 1. Neutron turns into a proton forming a new element 2. Atomic number increases by 1 3. Mass number stays the same 4. Electron (beta particle) is emitted http://library.thinkquest.org/3471/radiation_types_body.html

7. Nuclear Change Alpha Decay • Stabilization of nuclei by losing alpha particles • Alpha particle: helium nucleus • 2 protons and 2 neutrons From: http://library.thinkquest.org/3471/radiation_types_body.html

8. Nuclear Change Why does alpha decay happen? • If a nucleus contains too many protons, then excessive repulsion of like charges occurs • In an attempt to stabilize the nucleus, an alpha particle is emitted • The nucleus splits in two pieces: • One piece: alpha particle • Second piece: a nucleus reduced by two protons and two neutrons

9. Nuclear Change Result of Alpha Decay: 1. Atomic numbers decreases by 2 – new element is formed 2. The mass number has decreased by 4 amu 3. Alpha particle goes zooming away from the original nucleus

10. Nuclear Change Gamma Rays – Electron Capture • Produced when a proton “captures” an electron from the orbital nearest the nucleus and changes into a neutron • Decreases the atomic number by one • This process causes an “excited nucleus” • A gamma ray is emitted by the nucleus to become more stable

11. Nuclear Change Electron is absorbed by the nucleus Gamma Ray Proton turns into a neutron Result: 1. Atomic number decreases by one to form a new element 2. Mass number stays the same 2. Gamma ray is released From: http://library.thinkquest.org/3471/radiation_types_body.html

12. Nuclear Change Gamma Rays – Positron Emission • Positron – antiparticle of the electron! • The opposite of an electron • Proton emits a positron and becomes a neutron • The positron seldom makes it out of the atom because it collides with an electron , ANNIHILATION OF MATTER OCCURS • All the mass of the two particles are converted into gamma rays

13. Nuclear Change Proton gives off a Positron and becomes a neutron Positron is usually annihilated by an electron Results of positron emission: 1. Proton becomes a neutron 2. Atomic number changes 3. Element changes 4. Mass number stays the same 5. Positron emitted, but annihilated by an electron 6. Gamma rays given off

14. Nuclear Change Nuclear Equations MUST BE BALANCED! Due to the Laws of Conservation of Mass and Energy! • Mass numbers must be the same on both sides • Total atomic numbers must be the same on both sides (nuclear charges must balance) • If atomic number changes, the identity of the element must change