How do you determine if you have a covalent bond?

If the electronegativity difference (usually called ΔEN) is less than 0.5, then the bond is nonpolar covalent. If the ΔEN is between 0.5 and 1.6, the bond is considered polar covalent. If the ΔEN is greater than 2.0, then the bond is ionic.

Explanation:

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the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.