7 1 properties of radiation

The nucleus of an atom contains protons and neutrons.

Electrons are found orbiting the nucleus.

False. Most of the mass of an atom is concentrated in the nucleus. Electrons have a negligible mass compared to protons and neutrons.

The charge on the nucleus is positive.

False. An atom is neutral because it has an equal number of protons and electrons.

The atomic number of an atom is the number of protons in its nucleus. This number defines the chemical element.

The mass number of an atom is the total number of protons and neutrons in its nucleus.

In nuclear notation: Therefore, Z = number of protons = number of electrons, and A - Z = number of neutrons.

The mass number (top number) of carbon is 12. The atomic number (bottom number) of carbon is 6.

The mass number (top number) of beryllium is 9. The atomic number (bottom number) of beryllium is 4. Therefore, an atom of beryllium contains 4 protons, 5 neutrons and 4 electrons.

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.

False. An element can have more than one isotope.

False. Two different isotopes of uranium have the same number of protons but a different number of neutrons.

False. The atoms , , , are not possible isotopes of chlorine as they have the same mass number but different atomic numbers. Isotopes of an element must have the same atomic number but different mass numbers.

True. The atoms , , , are all possible isotopes of iron as they have the same atomic number but different mass numbers.

Some nuclei emit radiation because they are unstable due to having an imbalance of protons or neutrons.

The three types of radiation that a nucleus can emit are:

True. The emission of radiation from a nucleus is a spontaneous and random process.

An alpha particle is composed of two protons and two neutrons. It is equivalent to a helium nucleus.

A beta particle is a fast-moving electron.

Gamma radiation is a type of high-energy electromagnetic wave.

False. Alpha particles have a charge of +2 due to having two positively charged protons. It is beta particles that have a charge of -1 due to the negatively charged electron.

Alpha particles are the most ionising form of nuclear radiation. Beta particles are next, and gamma radiation is the least ionising.

The types of nuclear radiation in order of increasing penetrating power are:

An isotope will decay into a new element if the number of protons changes. Therefore, alpha and beta decay will produce a new element.

Alpha decay results in the mass number decreasing by 4, because 4 nucleons are emitted.

True. A neutron changes into a proton and an electron during beta decay. The high-energy electron is emitted from the nucleus.

Alpha decay results in the atomic number decreasing by 2, because 2 protons are emitted.

Gamma decay has no effect on the mass number or the atomic number. Gamma radiation reduces the energy of the nucleus but has no effect on the number of particles.

The atomic number increases by 1 as a result of beta decay. A neutron changes into a proton and an electron. The extra proton causes the atomic number to increase by 1, so a new element is formed.

The charge on a nucleus will decrease by 2 after it emits an alpha particle because 2 protons are emitted.

The mass number remains unchanged by beta decay. A neutron changes into a proton which has the same mass. A beta particle is emitted but this change in mass is negligible.

Ionising radiation can be detected using:

Background radiation is the radiation that exists around us all the time.

False. Radiation is a natural phenomenon that has always existed on Earth and in outer space.

Natural sources of background radiation include:

False. ** Ionising **radiation can be measured using a detector connected to a counter.

Count rate is measured in counts per second or counts per minute.

False. A corrected count rate can be calculated by subtracting the count rate found with no radioactive source present from the count rate with the radioactive source present.

The count rate decreases as the detector moves further from the radiation source.