Atomic structure

• How big is an atom?

  has a radius of about 1 × 10-10 metres
• What is the mass of a proton?

  1
• What is the mass of a neutron?

  1
• What is the mass of an electron?

  1/2000 (nearly zero)
• What is the charge on a proton?

  +1
• What is the charge on an electron?

  -1
• What is the charge on a neutron?

  0
• Where are protons found?

  in the nucleus of the atom
• Where are neutrons found?

  in the nucleus of the atom
• Where are electrons found?

  in energy levels orbiting the nucleus
• What happens to electrons when they absorb or emit radiation?

  it increases or decreases the distance from the nucleus respectively
• What is the atomic number?

  the number of protons
• What is the mass number?

  the number of protons and neutrons
• How do you find the number of protons an atom has?

  the bottom number next to the element
• How do you find the number of electrons an atom has?

  same as the number of protons
• How do you find the number of neutrons an atom has?

  mass number - atomic number
• Why do atoms have no overall charge?

  they have the same number of protons and electrons so the opposite charges cancel out
• How do ions get charged?

  by an atom gaining or losing electrons
• What is an isotope?

  atoms of the same element with the same number of protons but different number of neutrons
• What was the plum-pudding model?

  an idea of the possible structure of the atom based on observations by JJ Thomson. He suggested that the atom is a ball of positive charge with negative electrons embedded in it
• What did Rutherford do?

  The Alpha particle scattering experiment. This led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged.

  This nuclear model replaced the plum pudding model
• What did Bohr do?

  adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.
• What did Chadwick do?

  provided the evidence to show the existence of neutrons within the nucleus.
• What is radioactive decay?

  Some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable.
• What are the units for radioactivity?

  becquerel (Bq)
• What are the different types of radiation to be emitted?

  alpha particle (α), beta particle (β), gamma ray (γ), neutron (n)
• what is an alpha particle?

  this consists of two neutrons and two protons, it is the same as a helium nucleus
• what is a beta particle?

  a high speed electron ejected from the nucleus as a neutron turns into a proton
• How might an alpha particle be represented in a nuclear equation?

  
• How might a beta particle be represented in a nuclear equation?

  
• what is a gamma ray?

  electromagnetic radiation from the nucleus
• what is half-life?

  The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve.
• what is radioactive contamination?

  the unwanted presence of materials containing radioactive atoms on other materials
• what is irradiation?

  the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.
• How big is the nucleus

  The radius of a nucleus is less than 1/10000 of the radius of an atom