First 175 words of the document:
To have a full outer shell, atoms sometimes need to lose or gain an electron. To do this, they must
bond with another atom.
Metal atoms become positively charged by losing an electron whereas non-metal atoms become
negatively charged by gaining an electron.
Dot & cross diagrams
Dots are for metals, and crosses are for non-metals.
The dot in the chloride ion shows the electron that was taken from the sodium ion.
This is why a sodium ion had a charge of +1 & and a chloride ion is -1.
Electrons have a negative charge so if one leaves, the atom will still have the same amount of
positive protons & will be positive. It's the same if an atom gains an electron, but it becomes
It's the same if an atom needs to lose 2 electrons. The only difference is the magnesium ion has a
charge of +2 & the oxide ion has a charge of -2.
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Sometimes an atom needs to lose or gain 2 electrons. But if another electron only needs to lose or
gain one, 2 atoms with 1 electron spare or needed could bond with an atom that needs to lose or
gain 2. This has happened with calcium and chlorine to create 1 calcium ion & 2 chloride ions.…read more