Therefore molecular compounds have a fairly low

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therefore molecular compounds have a fairly low boiling point and a low melting point because a ll you have to do is overcome the relatively weak intermolecular forces ELECTRONEGATIVITY AND BOND POLARITY one problem with the lewis structures is that it tends to represent atoms as being equally shared when this is not the case for example, instead of representing hydrogen flouride as it should be represented as to demonstrate the true location of electrons the side that the arrow points toward is the negative side, while the side with the origin of the arrow is the partially positive charge similarly delta plus represents a partially positive charge while delta minus represents the opposite this partial charge on atoms does not make the bond ionic because the electrons are not practically transferred as they are in ionic compounds in HF however, the electrons are unequally shared the electron density is greater on the fluorine side than it is on the hydrogen side bonds with unequal sharing of electrons are said to be polar because there is a positive pole and a negative pole a polar covalent bond is intermediate between a pure covalent bond and an ionic bond pure covalent bonds and ionic bonds are two extremes within a broad continuum most covalent bonds between different atoms are actually polar covalent , somewhere between the ionic and pure covalent extremes
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ELECTRONEGATIVITY the ability of an atom to attract electrons to itself in a chemical bond is known as its electronegativity for example, fluorine is more electronegative than hydrogen because it takes a greater share of the electron density in a HF molecule the bond energy is the energy required to break a bond instead of it being the average of two bonding atoms it tends to be greater than the average this greater than average energy is due to the ionic character of the bond electronegativity can generally be displayed as a pattern across the periodic table:
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there are general trends in electronegativity in the period table: electronegativity generally increases across a period in the periodic table electronegativity generally decreases down a column in the periodic table Fluorine is the most electronegative element Francium is the least electronegative element generally electronegativity is inversely related to atomic size - the larger the atom, the less ability it has to attract electrons to itself in an electron bond
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BOND POLARITY, DIPOLE MOMENT, AND PERCENT IONIC CHARACTER the degree of polarity depends on the electronegativity difference between the two bonding elements the greater the electronegativity difference the more polar the bond if two elements with identical electronegativities form a covalent bond they share the electrons equally the resulting bond is purely covalent or nonpolar e.g. Cl2 if a bond forms between a metal and a nonmetal there is generally a large
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