Calcium chloride
3 marks · Normal(a) Lithium fluoride is formed when a lithium atom reacts with a fluorine atom. Each atom transfers electrons to form ions.
Draw a dot-and-cross diagram to show the ionic bonding in lithium fluoride. Label each ion clearly and show the charges.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Must show: Li atom has one outer electron (dot or cross), F atom has seven outer electrons (other symbol), Clearly shows one electron transferred from Li to F, Ions shown in square brackets with their charges (+ for Li, - for F), Correct charges (Li+, F−) written as superscripts, All electrons shown in outer shells
Also accept: Electrons indicated with consistent symbols (dots/crosses swapped is acceptable if clear)
Common mistakes: Incorrect charge on ions; Missing square brackets; Not showing electron transfer
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Recognises that 1 electron is transferred from lithium to fluorine and shows two full outer shells for resulting ions.
A1 · 1 mark · Shows correct number and placement of electrons (dot and cross convention) for each ion.
A2 · 1 mark · Shows correct charges and uses square brackets for each ion (Li+ and F−).
Worked solution
Draw a dot-and-cross diagram with:
- Lithium ion (Li⁺): a small circle with no electrons in its outer shell (since Li loses its single outer electron). Place a '+' charge as a superscript and a square bracket around the ion.
- Fluoride ion (F⁻): a larger circle nearby. Draw 8 outer electrons (7 crosses for F's own, 1 dot for the electron gained from Li if you show this convention) in the outer shell. Draw a '-' charge as a superscript and a square bracket.
- The transferred electron is a dot (or cross) that moves from Li to F in your arrangement.