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The Chemical Bond: Covalent vs. Ionic and Polar vs. Nonpolar

professor Dave here, let's learn about chemical bonds

a molecule is made up of atoms that are participating in chemical bonds with one another. there are

different types of bonds that we will want to be able to describe and the key

to their formation has to do with the difference in electronegativity between

the two atoms participating in the bond. if the difference is more than about 2

like with sodium and chlorine, chlorine will steal an electron from sodium

chlorine really wants another electron, sodium really wants to get rid of one so

everybody wins. the result is a positively charged sodium ion and a

negatively charged chloride ion. particles of opposite charge have an

electrostatic attraction so these two ions hang out together by forming an

ionic bond. this is a very strong attraction because it is happening

between ions that have a formal charge. bond, ionic bond. electrons taken not

shared. speaking of shared electrons if the difference in electronegativity

between the two atoms is less than about 1.7 no electrons are stolen but instead

the two atoms share two electrons. the electron from this atom feels the

attraction from the other nucleus and so does the electron from this atom, so the

atoms share the two electrons to form a covalent bond. covalent bonds can be

polar or nonpolar. if the electronegativity difference between the

atoms is not high enough to cause ionization but is at least more than

0.5, like with hydrogen and chlorine, instead of completely stealing the

electron the chlorine will just sort of hog the electrons in the resulting

covalent bond. the more electronegative atom in a polar covalent bond pulls the

electron density towards itself and as a result of the slight electron excess we

call this atom partially negative, denoted by the symbol Delta minus. the

atom whose electron is getting pulled away is slightly electron deficient and

therefore partially positive or Delta plus. if the electronegativity difference

is less than 0.5 the covalent bond is said to be

non polar. in a nonpolar covalent bond the electrons are shared more or less evenly

or in the case of two atoms of the same element, precisely evenly. the atoms will

have no partial charges at all. other than strange phenomena like metallic

bonding these are the main ways atoms bind to one another

remember that you can predict the type of bond that will form between two

elements by comparing their electronegativites. if the difference

is very low, less than 0.5 or so, it will be a nonpolar covalent bond where the

electrons are shared evenly. between about 0.5 and 1.7 it'll be a polar

covalent bond with the electrons are shared but one atom holds them more

tightly. if above 2 or so one atom will simply steal an electron from the

other and you'll get ions that are joined by on ionic bond. thanks for

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