Radio activity Flashcards
(49 cards)
Geiger-Marsden experiment setup
A beam of α-particles is fired at a thin gold foil.
Most α-particles passed straight through. What does this show?
Most of the atom is empty space.
Very few α-particles deflected > 90°. What does this show?
The nucleus is small, dense, and positively charged.
What is the conclusion of the Geiger-Marsden experiment?
Atoms have a small, dense, positively charged nucleus, and most of the atom is empty space.
What is nucleon number?
Total number of protons and neutrons.
What is proton (atomic) number?
Total number of protons.
What is an isotope?
Atoms of the same element with different numbers of neutrons but the same number of protons.
Describe the simple model of the atom.
Nucleus made of protons and neutrons; electrons orbit in a cloud around it.
What is nuclide notation?
A = nucleon number, Z = proton number, X = element symbol.
What is 1 unified atomic mass unit (u)?
1/12 the mass of a carbon-12 atom.
What is conserved during nuclear processes?
Nucleon number, proton number, and mass-energy.
Why is radioactive decay called random?
Each nucleus has equal probability to decay at any time; it can’t be predicted.
Why is radioactive decay called spontaneous?
It is not affected by external conditions like temperature or pressure.
How does a graph show randomness in decay?
Fluctuations in count rate.
How does a graph show spontaneity in decay?
Same decay pattern at different conditions (e.g., temperature, pressure).
What is an α-particle?
Helium nucleus (2 protons, 2 neutrons).
What is a β-particle?
Fast-moving electron or positron.
What is a γ-ray?
Electromagnetic radiation (photon).
Relative mass of α, β, and γ?
α: 4, β: 1/1840, γ: 0
Charge of α, β, and γ?
α: +2, β: -1, γ: 0
Speed of α, β, and γ?
α: ~10^6 m/s, β: ~10^8 m/s, γ: speed of light (~3×10^8 m/s)
Which radiation has highest ionizing power?
α-particles
Which radiation is most penetrating?
γ-rays
α-particles are stopped by?
Paper
