Atomic Structure and the Periodic Table
What's covered
Key facts
Argon is used in (incandescent) light bulbs as an inert filler that stops the hot tungsten filament burning.
Alkali metals are stored under oil to prevent them reacting with air and water.
Down Group 7, boiling points increase as molecules get larger and intermolecular (London) forces strengthen.
Chlorine has two stable isotopes, ³⁵Cl (~75%) and ³⁷Cl (~25%), giving Ar = (35 × 0.75) + (37 × 0.25) = 35.5.
An atom has no overall charge because the number of protons (+1 each) equals the number of electrons (−1 each).
The atomic number of an atom is the number of protons it contains.
Ordering by atomic number resolved anomalies that mass-order produced (e.g. tellurium/iodine).
Argon is used in light bulbs because the inert atmosphere protects the filament from oxidising.
Group 1 metals become more reactive down the group because there are more shells: the outer electron is further from the nucleus and shielded by inner electrons.
Bromine is a liquid at room temperature.
Sample questions
A taste of the 92 questions in this topic — answers marked. Sign up to practise the full set with spaced repetition.
Which is a correct use of a noble gas?
- ✓Argon in light bulbs (inert filler stops the filament burning)
- •Argon in scuba diving tanks (cheap inert filler)
- •Helium in tungsten light bulbs (cheap inert atmosphere)
- •Krypton in shop window signs (orange light)
What are the products when potassium reacts with cold water?
- •Potassium carbonate and carbon dioxide
- •Potassium chloride and oxygen
- ✓Potassium hydroxide solution and hydrogen gas
- •Potassium oxide and water
Why does reactivity decrease going down Group 7?
- •Atoms become larger and hold more electrons, so they need fewer extras
- •Higher melting/boiling points make the elements less likely to react with metals
- •More protons in the nucleus pull electrons inwards, making the atom too stable
- ✓Outer shell is further, more shielded — harder to attract an electron
What are isotopes?
- •Atoms of different elements with the same mass number
- ✓Atoms of the same element with different numbers of neutrons
- •Atoms of the same element with different numbers of protons
- •Ions of the same element with different numbers of electrons
Where are the three subatomic particles found in an atom?
- •Electrons in the nucleus; protons and neutrons in outer shells
- ✓Protons and neutrons in the nucleus; electrons in shells around it
- •Protons in the nucleus; neutrons and electrons in the shells
- •Protons, neutrons, and electrons all in the nucleus
What did Rutherford's gold foil experiment demonstrate about atomic structure?
- ✓Atom is mostly empty space with a tiny, dense, positively charged nucleus
- •Atoms contain equal numbers of protons and neutrons in the nucleus
- •Electrons orbit the nucleus in fixed shells (this was Bohr's contribution)
- •The nucleus contains both positive and negative particles that partly cancel
Try it for four weeks. Free.
One school. Unlimited classes. No card limit. No teacher limit. If your students aren't practising daily by the end of the trial, you owe us nothing.