2-2 Atoms And Covalent Bonds

Atoms and Covalent Bonds Chapter 2, Section 2

Electron Sharing Fluorine dot bond F2 pic

Covalent bond- a chemical

bond formed when 2 atoms share electrons Covalent bond- both atoms attract the two shared electrons at the same time

How Many Bonds? •The number of bonds these atoms can form equals the number of valence electrons needed to make a total of eight. •Double bond- two pairs of electrons are shared between atoms •Example: CO2 •Hydrogen is the exception! It has no more than 2 electrons and forms 1 bond.

Physical Properties of Molecular Molecular compounds- consist of molecules having covalently bonded atoms Forces holding molecular solids together are much weaker than those of ions Most molecular compounds are poor conductors of electricity because no charged particles are available to move

Unequal Sharing of Electrons Non-polar molecules Polar Molecules Some atoms pull more

Non-polar - valence

strongly on the shared electrons are shared electrons than other equally atoms do. As a result, A molecule is non-polar if electrons move closer to it contains polar bonds one atom, causing the that cancel each other. atoms to have a slight CO2 electrical charges Unequal sharing makes on F2 is non-polar atom slightly negative and the other slightly positive. A covalent bond in which electrons are shared unequally is polar.

Attractions between Molecules Differences in the attractions between molecules lead to different properties in polar and non-polar compounds Water- surface tension due to polarity Oil and water don’t mix due to non-polarity and polarity Washing laundry benefits from polarity