Twinkl Atomic Structure

What is the approximate size of the radius of an atom?

• 1 × 10^-5 metres

• 1 metre

• 1 × 10^10 metres

• 1 × 10^-10 metres

Which statement about atoms is true?

• atoms have a positive charge

• the number of electrons in an atom is equal to the number of protons in the nucleus of that atom

• there are more electrons in an atom than there are protons in the nucleus of that atom

• there are fewer electrons in an atom than there are protons in the nucleus of that atom

If an atom loses one or more of its outer electrons, what happens to its overall charge?

• it becomes negative

• it becomes positive

• stays the same

• depends on the ion

The discovery of the electron led to which model of the atom?

• fruit cake model

• treacle sponge model

• jam tart model

• plum pudding model

Which of the following best describes radioactive decay?

• a random process by which a stable atomic nucleus remains stable

• a random process by which an unstable atomic nucleus gives out radiation as it changes to become more stable

• a controlled process by which a stable atomic nucleus gives out radiation as it changes to become unstable

• a controlled process by which a stable atomic nucleus remains stable

What is emitted from the nucleus of an atom during alpha decay?

• an electron

• a hydrogen nucleus

• a helium nucleus

• a proton

Which of the following is the best definition for the half-life of a radioactive isotope?

• the time it takes for half of the atoms in a substance to become unstable

• the time it takes for half of the atoms in a substance to disappear

• the time it takes for the number of radioactive nuclei in a sample of the isotope to halve

• the time it takes for half of the isotopes in a sample to become charged

Answer explanation

The other answer choices are incorrect because:

• The time it takes for half of the atoms in a substance to become unstable is not a valid definition, because radioactive atoms are already unstable by nature. They do not become unstable over time, they decay into more stable atoms¹²

• The time it takes for half of the atoms in a substance to disappear is not a valid definition, because radioactive atoms do not disappear when they decay. They transform into different atoms, which may or may not be radioactive themselves. The total number of atoms in a sample remains constant, but the number of radioactive atoms decreases¹²

• The time it takes for half of the isotopes in a sample to become charged is not a valid definition, because radioactive isotopes do not become charged when they decay. They emit different types of radiation, such as alpha, beta, or gamma rays, which may or may not change the charge of the resulting atoms. The charge of an atom depends on the number of protons and electrons, not on the radioactivity¹²

Which of the following best describes irradiation?

• the radioactive decay of a substance

• a method of clearing away radioactive waste

• the process of making an object radioactive

• the process of exposing an object to nuclear radiation

Which of the following is an example of nuclear radiation?

• alpha radiation

• beta radiation

• gamma radiation

• all of the above