The protons, neutrons and electrons in an atom, comparing their mass and charge, why atoms are neutral and stable, A = Z + N, nuclide notation, isotopes and the shell model.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Carbon-12 and carbon-14 are both carbon, but one is stable and the other is radioactive and can be used to date ancient bones. The only difference is two neutrons.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
+1; relative mass 1; in the nucleus.
0 charge; relative mass 1; in the nucleus.
−1; relative mass 1/1 840; in shells.
Protons = electrons.
Number of protons.
A = Z + N (protons + neutrons).
ᴬ_Z X.
Same Z, different N (same element, different mass).
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Physics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [15 marks]
A neutral atom of radium-226 has atomic number 88.
(a) (a) State the number of protons and electrons in the neutral atom. [2]
(b) (b) Calculate the number of neutrons in the nucleus. [2]
(c) (c) Explain the term isotope. [2]
(d) (d) Write the nuclide notation for an isotope of radium with 140 neutrons. [2]
(e) (e) Explain why an atom is normally neutral. [2]
(f) (f) Compare the mass and charge of the electron with the proton. [3]
(g) (g) State the electron arrangement of an atom with atomic number 11 and name its group. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.