Basic Ideas About Atoms

What Basic Ideas About Atoms covers

Basic Ideas About Atoms is examined on AS Unit 1 of WJEC Chemistry, The Language of Chemistry, Structure of Matter and Simple Reactions. 144 recall questions across 9 subtopics.

The 9 subtopics

Each one has its own page. WJEC AS Chemistry students sit this topic in the first year.

• Radioactive decay and nuclear equationsRecall questions on Radioactive decay and nuclear equations.Open →
• Alpha, beta and gamma radiationRecall questions on Alpha, beta and gamma radiation.Open →
• Half-life, dating and the uses of radioisotopes: half-life of radioactive decayRecall questions on half-life of a radioactive isotope.Open →
• Half-life, dating and the uses of radioisotopes: adverse consequences for living cellsFourteen recall questions on half-life, dating and the uses of radioisotopes: adverse consequences for living cells.Open →
• Ionisation energies and electronic structureRecall questions on Ionisation energies and electronic structure.Open →
• Orbitals and the filling of sub-shellsRecall questions on electron configuration of a bromine atom.Open →
• Atomic spectra and the energy of light: atomic emission spectrum of the hydrogen atomTwelve recall questions on atomic spectra and the energy of light: atomic emission spectrum of the hydrogen atom.Open →
• Atomic spectra and the energy of light: relationship between energy and frequencyRecall questions on relationship between energy and frequency.Open →
• Atomic spectra and the energy of light: significance of the frequencyTwelve recall questions on atomic spectra and the energy of light: significance of the frequency.Open →

What you need to know

Answer each one before you reveal it.

Take Basic Ideas About Atoms further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Mass number vs Atomic number

  Mass number: the total number of protons and neutrons in a nucleus. Atomic number: the number of protons, which fixes which element it is.

• First ionisation energy vs Second ionisation energy

  First ionisation energy: the energy to remove one electron from each atom in a mole of gaseous atoms. Second ionisation energy: the energy to remove a further electron from each resulting unipositive ion.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What makes a nucleus radioactive?

   Model answer

   The nucleus is unstable, usually because the ratio of neutrons to protons lies outside the band of stability or because the nucleus is simply too large. It reaches a more stable arrangement by emitting a particle or a burst of energy, and this emission is what we detect as radioactivity.

2. 2

   Why is radioactive decay described as random and spontaneous?

   Model answer

   It is impossible to predict which particular nucleus in a sample will decay next or when, so the process is random. It is spontaneous because it happens of its own accord, without needing to be started, and its rate cannot be altered by heating, by pressure or by putting the element into a different chemical compound.

3. 3

   What is an alpha particle, and how does emitting one change the nucleus?

   Model answer

   An alpha particle is a helium nucleus, ⁴₂He, consisting of two protons and two neutrons. Emitting one lowers the mass number by 4 and the atomic number by 2, so the atom becomes an element two places earlier in the periodic table.

4. 4

   Radium-226 is an alpha emitter. Write the nuclear equation for its decay.

   Model answer

   ²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He. The mass numbers balance as 226 = 222 + 4 and the atomic numbers as 88 = 86 + 2.

5. 5

   What actually happens inside the nucleus when a beta-minus particle is emitted?

   Model answer

   A neutron converts into a proton and an electron. The proton stays in the nucleus while the electron is ejected at high speed as the beta particle. The nucleus therefore has one more proton and one fewer neutron than before.

6. 6

   How do the mass number and atomic number change during beta-minus decay?

   Model answer

   The mass number is unchanged, because a neutron has simply been replaced by a proton and the total number of nucleons stays the same. The atomic number rises by one, so the atom becomes the next element along in the periodic table.

What is inside Levo

Six ways to work the same material.

Basic Ideas About Atoms revision questions

Is Basic Ideas About Atoms examined at AS in WJEC Chemistry?

Yes. It sits in AS Unit 1, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.

What does Basic Ideas About Atoms cover in WJEC AS-Level Chemistry?

9 subtopics: radioactive decay and nuclear equations, alpha, beta and gamma radiation, half-life, dating and the uses of radioisotopes: half-life of radioactive decay, half-life, dating and the uses of radioisotopes: adverse consequences for living cells, ionisation energies and electronic structure, orbitals and the filling of sub-shells, atomic spectra and the energy of light: atomic emission spectrum of the hydrogen atom, atomic spectra and the energy of light: relationship between energy and frequency and atomic spectra and the energy of light: significance of the frequency. Each one has its own page with questions and model answers.

How is Basic Ideas About Atoms organised?

By the WJEC 1410QS specification, subtopic by subtopic, so it matches the order you are taught it in.