Science - Atoms & Radioactivity

What is the charge and mass of protons?

Protons have a positive charge and a mass of one.

What is the charge and mass of neutrons?

Neutrons have a neutral charge of zero and a mass of one.

What is the charge and relative mass of electrons?

Electrons have a negative charge and a relative mass of 1/2000 compared to protons and neutrons.

What is the approximate size of an atom?

About 10^-10 meters.

What is the approximate size of a nucleus?

About 10^-14 meters, which is roughly 10,000 times smaller than an atom.

What was the earliest idea of the atom?

The atom was thought to be a solid sphere, indivisible.

Who proposed the plum pudding model?

JJ Thompson.

How did the plum pudding model describe the atom?

As a ball of positive charge with electrons distributed evenly like chocolate chips in a muffin.

What experiment led to the development of the nuclear model?

The alpha scattering experiment conducted by Ernest Rutherford.

What did Rutherford conclude from the alpha scattering experiment?

Most of the atom is empty space, and there is a small, dense, positively charged nucleus.

What happens to alpha particles when they approach the nucleus?

They experience a repulsive force due to like charges, which can lead to deflection.

What was a key finding from the alpha scattering experiment?

Some alpha particles were deflected at large angles, indicating a dense positive region in the atom.

What does the nuclear model of the atom suggest about electron arrangement?

Electrons orbit around the nucleus in mostly empty space.

What is the Bohr model of the atom?

An extension of the nuclear model where electrons orbit at fixed energy levels or shells.

What happens when an electron absorbs electromagnetic radiation in the Bohr model?

The electron moves to a higher energy level or shell.

What occurs when an electron falls back to a lower energy level?

Electromagnetic radiation is emitted.

What is the significance of evidence in the development of atomic models?

New evidence from experiments can support or lead to the revision of existing models.

What was the main flaw in the plum pudding model according to Rutherford's findings?

It could not explain the deflection of alpha particles, which indicated a dense nucleus.

What does the term 'fixed orbits' refer to in the Bohr model?

Electrons can only orbit at specific energy levels, not just anywhere around the nucleus.

Why is it incorrect to say that the plum pudding model was disproven?

It is more accurate to say that new evidence did not support it, leading to the development of a new model.

What happens when an electron moves to a lower energy level?

Electromagnetic radiation is emitted, indicating that the electron has lost energy.

Who discovered the neutron?

James Chadwick

What is the atomic number of an element?

The number of protons in the nucleus.

How do you calculate the mass number of an atom?

By adding the number of protons and neutrons.

What defines an isotope?

Atoms of the same element with the same number of protons but different numbers of neutrons.

What is an ion?

An atom that has gained or lost one or more electrons, resulting in a net charge.

What is the difference between activity and count rate?

Activity is the actual number of decays per second in a radioactive source, while count rate is the number of decays measured per second.

What type of radiation is emitted by unstable nuclei?

Alpha, beta, or gamma radiation.

What is the range of alpha radiation in air?

About 5 cm.

What material can stop alpha radiation?

Anything as thin as paper.

How ionizing is alpha radiation?

Very ionizing.

What is the range of beta radiation in air?

Up to 1 meter.

What material can stop beta radiation?

A thin sheet of aluminum.

How ionizing is beta radiation?

Moderately ionizing.

What is the range of gamma radiation?

It can travel many kilometers, effectively infinite range.

What material can stop gamma radiation?

Very thick lead or concrete.

How ionizing is gamma radiation?

Weakly ionizing.

What is the composition of an alpha particle?

Two protons and two neutrons.

What is the relationship between ionization and the range of radiation?

Higher ionization leads to a shorter range as energy is lost quickly.

What is a Geiger-Müller tube used for?

To detect radiation and measure the count rate.

What is the unit of measurement for activity in radioactive sources?

Becquerels (Bq).

What happens to an atom when it becomes an ion?

It gains a positive charge if it loses electrons or a negative charge if it gains electrons.

What is carbon-14 known for?

It is radioactive and has an unstable nucleus.

What is the significance of a radioactive nucleus being unstable?

It leads to the emission of radiation.

How do you determine the number of neutrons in an atom?

By subtracting the atomic number from the mass number.