How atoms share electrons to form covalent bonds, dot-and-cross diagrams for common molecules (single, double and triple bonds), writing molecular formulae and the properties of simple molecular substances.
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.
Water, oxygen and sugar contain no metals at all. Their atoms hold on to each other by sharing electrons rather than swapping them.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Pick a molecule and rotate it. Check the bond angles and the number of bonds on each atom.
Copy these into your notebook in your own words — that is how they stick.
Sharing of a pair of electrons between non-metal atoms.
One / two / three shared pairs.
Two shared pairs, two lone pairs on O.
Three shared pairs, one lone pair on N.
Four shared pairs.
Two C=O double bonds.
Valence shells only; dots for one atom, crosses for the other.
Low melting points; non-conductors; weak forces between molecules.
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 Chemistry 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]
Hydrogen (atomic number 1) reacts with sulfur (atomic number 16) to form hydrogen sulfide, H₂S.
(a) (a) Draw the arrangement of electrons in a sulfur atom. [2]
(b) (b) Using valence shells only, draw a dot-and-cross diagram for H₂S. [3]
(c) (c) State the type of bond and explain how it forms. [2]
(d) (d) Draw dot-and-cross diagrams for (i) water and (ii) nitrogen. [4]
(e) (e) Explain why H₂S has a low melting point. [2]
(f) (f) State whether H₂S conducts electricity and why. [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.