← Chemistry / 1 Inorganic Chemistry
1.2 The Atom
Chemistry · Grade 10 · 24 lessons in the design
What you will be able to do
- describe the structure of an atom
- state the charge and relative mass of protons, neutrons and electrons
- work out the number of subatomic particles from atomic and mass numbers
- draw the electron arrangement of the first twenty elements
Key questions
“What is everything around us made of?”
Lessons
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Inside the atom
40 min · 2 practice tasks · quizWhat an atom is made of, and how the three particles differ.
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Atomic number and mass number
40 min · 2 practice tasks · quizHow to work out how many of each particle an atom has.
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The proton: identity of an element
40 min · 1 practice tasks · quizWhy the number of protons is the one number that decides which element you have.
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The neutron: mass without charge
40 min · 1 practice tasks · quizNeutrons add mass and help hold the nucleus together, without changing the element.
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The electron: where chemistry happens
40 min · 1 practice tasks · quizElectrons are light, negative, and arranged in shells - they decide how an atom reacts.
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Comparing protons, neutrons and electrons
40 min · 1 practice tasks · quizOne table, used fluently: charge, mass, location, and what each particle controls.
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Why atoms have no overall charge
40 min · 1 practice tasks · quizEqual protons and electrons cancel; neutrons do not enter the charge sum.
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The nucleus and empty space
40 min · 1 practice tasks · quizAlmost all the mass is in a tiny nucleus; almost all the volume is empty.
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Writing atoms in nuclear notation
40 min · 1 practice tasks · quizRead A and Z on a nuclide symbol, and write sodium-23 as ^23^Na or with Z shown.
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Worked calculations of particle numbers
40 min · 1 practice tasks · quizA reliable method for protons, neutrons and electrons, including a first look at ions.
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Isotopes: same element, different mass
40 min · 1 practice tasks · quizIsotopes have the same proton number and different neutron numbers.
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Hydrogen, carbon and chlorine isotopes
40 min · 1 practice tasks · quizThe isotopes you must recognise, and one everyday use of each story.
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Relative atomic mass as a weighted average
40 min · 1 practice tasks · quizHow Cl-35 and Cl-37 become 35.5 on the periodic table.
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Energy levels around the nucleus
40 min · 1 practice tasks · quizElectrons occupy shells of different energy; the first four matter for the first twenty elements.
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Filling shells: the 2,8,8,2 rule
40 min · 1 practice tasks · quizA routine for turning an electron count into an arrangement, with the common traps.
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Electron arrangement of hydrogen to neon
40 min · 1 practice tasks · quizThe first ten elements, shells 1 and 2, and the first noble gas.
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Electron arrangement of sodium to calcium
40 min · 1 practice tasks · quizElements 11 to 20: the third shell, then potassium and calcium on a fourth.
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How to draw atoms
40 min · 1 practice tasks · quizA five-step Bohr diagram: nucleus labels, then electrons on shells.
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Valence electrons
40 min · 1 practice tasks · quizThe outer-shell electrons are the ones that react; they are the last number in the arrangement.
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Atoms versus ions
40 min · 1 practice tasks · quizIons are atoms that have lost or gained electrons; the proton number does not change.
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How the model of the atom changed
40 min · 1 practice tasks · quizDalton, Thomson, Rutherford and Bohr: each model answered an experiment the previous one could not.
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Radioactivity: an awareness
40 min · 1 practice tasks · quizSome nuclei are unstable; know the three names, simple shielding, and where the full topic lives.
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Building models of atoms
40 min · 1 practice tasks · quizMake physical models of the first twenty with beads and wire, and say what the model gets wrong.
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Putting the atom together
40 min · 1 practice tasks · quizGiven A and Z, name the element, count particles, write the arrangement, and draw or model it.