AQA GCSE Combined Science: Trilogy · 5.1

Atomic structure and the periodic table

Revision questions with answers for 5.1 Atomic structure and the periodic table in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All questions and answers

Question 1 · Spec 5.1.1.1
What is an atom?
Answer:
The smallest part of an element that can exist while retaining that element's identity.
Question 2 · Spec 5.1.1.1
What is an element?
Answer:
A substance containing only one type of atom, identified by its number of protons.
Question 3 · Spec 5.1.1.1
How is a compound different from an element?
Answer:
A compound contains two or more different elements chemically combined in fixed proportions.
Question 4 · Spec 5.1.1.1
What does the formula H₂SO₄ tell you?
Answer:
Each molecule contains two hydrogen atoms, one sulfur atom and four oxygen atoms.
Question 5 · Spec 5.1.1.1
How do chemical reactions differ from physical changes?
Answer:
Chemical reactions rearrange atoms to form new substances. Physical changes do not form new substances.
Question 6 · Spec 5.1.1.2
How is a mixture different from a compound?
Answer:
Its substances are not chemically bonded together, retain their properties and can be separated by physical processes.
Question 7 · Spec 5.1.1.2
How can an insoluble solid be separated from a liquid?
Answer:
Filtration: the solid remains as residue and the liquid passes through as filtrate.
Question 8 · Spec 5.1.1.2
How can crystals be obtained from a solution?
Answer:
Evaporate some solvent, allow the concentrated solution to cool and crystallise, then separate and dry the crystals.
Question 9 · Spec 5.1.1.2
How does simple distillation recover a solvent?
Answer:
Heat the solution to vaporise the solvent, then cool its vapour in a condenser to collect liquid solvent.
Question 10 · Spec 5.1.1.2
When is fractional distillation useful?
Answer:
For separating a mixture of liquids with different boiling points, using repeated vaporisation and condensation.
Question 11 · Spec 5.1.1.2
What separation method can distinguish dyes in an ink?
Answer:
Chromatography, because different dyes travel differently with the solvent through the stationary phase.
Question 12 · Spec 5.1.1.3
Why do scientific models of the atom change?
Answer:
New experimental evidence can reveal weaknesses in a model and lead to its revision or replacement.
Question 13 · Spec 5.1.1.3
How did discovery of the electron change the atomic model?
Answer:
Atoms could no longer be considered indivisible; they contained smaller negatively charged particles.
Question 14 · Spec 5.1.1.3
Describe the plum pudding model.
Answer:
Negatively charged electrons embedded in a spread-out ball of positive charge.
Question 15 · Spec 5.1.1.3
What were the main alpha-scattering observations?
Answer:
Most alpha particles passed through the foil; some were deflected; a very small number bounced back.
Question 16 · Spec 5.1.1.3
What did alpha scattering reveal about the atom?
Answer:
It is mostly empty space, with most mass and positive charge concentrated in a small nucleus.
Question 17 · Spec 5.1.1.3
How did Bohr modify the nuclear model?
Answer:
He proposed that electrons occupy specific energy levels at particular distances from the nucleus.
Question 18 · Spec 5.1.1.3
What did James Chadwick's work establish?
Answer:
The existence of neutrons within the nucleus.
Question 19 · Spec 5.1.1.4
State the relative charges of protons, neutrons and electrons.
Answer:
Proton: +1; neutron: 0; electron: -1.
Question 20 · Spec 5.1.1.5
State the relative masses of protons, neutrons and electrons.
Answer:
Proton and neutron: about 1 each; electron: very small, about 1/1836.
Question 21 · Spec 5.1.1.4
Why is a neutral atom uncharged overall?
Answer:
It contains equal numbers of protons and electrons, so positive and negative charges cancel.
Question 22 · Spec 5.1.1.5
What is atomic number?
Answer:
The number of protons in an atom's nucleus.
Question 23 · Spec 5.1.1.5
What is mass number?
Answer:
The total number of protons and neutrons in an atom's nucleus.
Question 24 · Spec 5.1.1.5
An atom has atomic number 11 and mass number 23. Count its particles.
Answer:
11 protons, 12 neutrons and, if neutral, 11 electrons.
Question 25 · Spec 5.1.1.6
What are isotopes?
Answer:
Atoms of the same element with the same number of protons but different numbers of neutrons.
Question 26 · Spec 5.1.1.6
Why is relative atomic mass often not a whole number?
Answer:
It is a weighted mean of the masses of an element's isotopes, accounting for their relative abundances.
Question 27 · Spec 5.1.1.6
An element is 75% mass-35 isotope and 25% mass-37 isotope. Find its relative atomic mass.
Answer:
(75 × 35 + 25 × 37) / 100 = 35.5.
Question 28 · Spec 5.1.1.5
What is the approximate radius of an atom?
Answer:
About 0.1 nm, or 1 × 10⁻¹⁰ m.
Question 29 · Spec 5.1.1.5
How does the nucleus's radius compare with the atom's?
Answer:
It is less than about 1/10,000 of the atom's radius; most atomic mass is concentrated there.
Question 30 · Spec 5.1.1.7
Give the electron arrangement of sodium, atomic number 11.
Answer:
2,8,1: two electrons in the first shell, eight in the second and one in the third.
Question 31 · Spec 5.1.2.1
How are elements ordered in the modern periodic table?
Answer:
By increasing atomic number, with elements having similar properties placed in the same groups.
Question 32 · Spec 5.1.2.1
What does an element's period tell you about its electrons?
Answer:
The number of occupied electron shells.
Question 33 · Spec 5.1.2.1
For Groups 1 and 7, what does the group number show?
Answer:
The number of electrons in the outer shell.
Question 34 · Spec 5.1.2.1
Why do elements in the same group have similar chemical properties?
Answer:
They have the same number of outer-shell electrons, which determine their chemical reactions.
Question 35 · Spec 5.1.2.3
How do metals and non-metals differ when forming simple ions?
Answer:
Metal atoms lose electrons to form positive ions; non-metal atoms gain electrons to form negative ions.
Question 36 · Spec 5.1.2.3
Where are most metals and non-metals found in the periodic table?
Answer:
Metals are mainly on the left and centre; non-metals are towards the right.
Question 37 · Spec 5.1.2.3
Why does sodium form Na⁺ rather than Na⁻?
Answer:
It loses its single outer electron to obtain a full outer shell, leaving one more proton than electrons.
Question 38 · Spec 5.1.2.2
Why did early periodic tables sometimes give inconsistent groupings?
Answer:
They ordered elements mainly by atomic weight before protons were known, and some elements had not yet been discovered.
Question 39 · Spec 5.1.2.2
How did Mendeleev improve the periodic table?
Answer:
He left gaps for undiscovered elements and sometimes changed atomic-weight order to keep elements with similar properties together.
Question 40 · Spec 5.1.2.2
Why did later discoveries support Mendeleev's table?
Answer:
New elements had properties close to those he predicted for the gaps.
Question 41 · Spec 5.1.2.4
Why are Group 0 elements unreactive?
Answer:
Their outer electron shells are full, giving stable electronic structures.
Question 42 · Spec 5.1.2.4
What is unusual about helium's full outer shell?
Answer:
It contains two electrons; the other Group 0 elements have eight in their outer shell.
Question 43 · Spec 5.1.2.4
How do Group 0 boiling points change down the group?
Answer:
They increase as relative atomic mass increases.
Question 44 · Spec 5.1.2.5
What do lithium, sodium and potassium have in common?
Answer:
They are Group 1 metals with one outer-shell electron and form +1 ions.
Question 45 · Spec 5.1.2.5
What are the products when a Group 1 metal reacts with water?
Answer:
A metal hydroxide and hydrogen; the resulting solution is alkaline.
Question 46 · Spec 5.1.2.5
Why does Group 1 reactivity increase down the group?
Answer:
The outer electron is farther from the nucleus and more shielded, so it is lost more easily.
Question 47 · Spec 5.1.2.6
Describe chlorine, bromine and iodine at room temperature.
Answer:
Chlorine is a green gas, bromine a red-brown liquid and iodine a dark solid.
Question 48 · Spec 5.1.2.6
How do Group 7 melting and boiling points change down the group?
Answer:
They increase as relative molecular mass increases.
Question 49 · Spec 5.1.2.6
Why does Group 7 reactivity decrease down the group?
Answer:
An incoming electron is farther from the nucleus and more shielded, so it is attracted less strongly.
Question 50 · Spec 5.1.2.6
What happens when chlorine is added to potassium bromide solution?
Answer:
Chlorine displaces bromine because it is more reactive: Cl₂ + 2KBr → 2KCl + Br₂.

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