To get a full outer shell, atoms lose or gain electrons.
Metals lose electrons to get a full outer shell and become positive ions.
Non-metals (usually) gain electrons to get a full outer shell and become negative ions.
Ionic bonding refers to the attraction between oppositely charged ions.
The greater the charge of the ions, the greater the attraction and the stronger the ionic bonding between the ions.
Atomic Structure Recap
We know that atoms have electrons that travel around a nucleus in ‘orbitals’ and exist in sub-shells. Each orbital can only hold one pair of electrons, and each sub-shell is a different distance from the nucleus (1 being the closest, 2 the nest closest, etc.).
Ionic bonding concerns the outermost electrons and sub-shell of an atom.
The most stable configuration for an atom is to have eight electrons in its outermost shell (octet rule). The reactivity of an element can often be linked to how easily an atom can ‘get’ to having eight electrons in its outermost shell. This explains why the noble gases (group 8 in the periodic table) are so unreactive, as they do not want to change.
With ionic bonding, electrons are lost or gained by atoms, enabling each atom to have a full outer shell.
Electrons are negatively charged. So, if a neutral atom loses an electron, it becomes a positive ion; if a neutral atom gains an electron, it becomes a negative ion.
Positive and negative ions will be attracted to each other (electrostatic attraction). This attraction is what holds ionic compounds together – there is no physical bond, but a strong attraction.
Ionic bonding exist when metals and non-metals are bonded together.
Metals always form positive ions (lose electrons); non-metals form negative ions (gain electrons).
The stronger the ionic charge (the charge on the ion - how many electrons an atom has gained or lost), the stronger the ionic bonding.
The group number (one to eight) in the periodic table tells us how many electrons an atom either needs to lose or gain to get to a full outer shell.