Students learn the structure of the atom and the charge and relative mass of protons, neutrons and electrons. They use atomic number and mass number to find the number of each particle, explain isotopes, write electron arrangements for the first 20 elements using the 2, 8, 8, 2 pattern and link the number of outer-shell electrons to how elements behave.
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Curriculum: Australian Curriculum. We show specific outcome codes only where they have been verified against the official curriculum document.
Completed: Atomic Structure: Protons, Neutrons, Electrons and Electron Shells
Year 9 students (typically ages 14–15) working on chemical sciences. It is pitched at level 2 · standard; a harder version is linked above.
Yes. The PDF includes a full answer sheet with model answers and success criteria where there is more than one good answer. You can also view the answers online.
About 40 minutes for 24 questions. Short, regular sessions work best: two or three a week beats one long one.
No. Click Download Free PDF and it opens immediately. It is free for personal, classroom and homeschool use.
Try The Periodic Table: Groups, Periods, Metals and Non-Metals.
Success TutoringWorksheetsYear 9 · Science · Chemical SciencesName
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Remember: atomic number = protons = electrons (in a neutral atom); neutrons = mass number − atomic number.
An atom has a tiny, dense nucleus containing protons and neutrons. Electrons move around the nucleus in energy levels called shells. Almost all of the mass of an atom is in its nucleus.
The atomic number is the number of protons. In a neutral atom, the number of electrons equals the number of protons. The mass number is the total number of protons and neutrons, so neutrons = mass number − atomic number.
For the first 20 elements, electrons fill the shells in order: up to 2 in the first shell, up to 8 in the second, up to 8 in the third, and then the fourth shell starts. Calcium, with 20 electrons, is 2, 8, 8, 2.
Example: an atom of sodium has atomic number 11 and mass number 23. It has 11 protons, 23 − 11 = 12 neutrons and 11 electrons, arranged 2, 8, 1.
For each neutral atom, write the number of protons, neutrons and electrons, and the electron arrangement.
Symbols always start with a capital letter; a second letter is lower case. Some symbols come from Latin names, such as Na (natrium) for sodium and K (kalium) for potassium.
Preview — the PDF contains the full resource and answer sheet.
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