Electronegativity and Forces

3 types of bonds There are three types of chemical bonds that can form between atoms: Ionic bonds Polar Covalent bonds (partly share electrons) Non-polar Covalent bonds (equally share electrons)

Electronegativity How do we measure how strong the atoms pull electrons = which of the 3 bond types is it? Electronegativity = measure of how strongly a specific element attracts electrons. Table on page 265 in textbook.

Electronegativity The bigger the electronegativity DIFFERENCE the more polar the bond. Process: Subtracting the electronegativity of one element versus one of another element.

Electronegativity Ranges: Less than 0.4 = nonpolar covalent Between 0.4 and 1.7 = polar covalent (partial ionic character) Greater than 1.7 = ionic

Showing a polar bond Isn’t a whole charge just a partial charge d+ means a partially positive d- means a partially negative The Cl pulls harder on the electrons The electrons spend more time near the Cl

Intermolecular Forces All atoms and molecules attract to each other, but vary by the amount of attraction London forces attract non-polar molecules or atoms together (non-polar means there are no partial charges within the molecule, i.e. covalent) Animation: http://antoine.frostburg.edu/chem/senese/101/liquids/faq/h-bonding-vs-london-forces.shtml

Intermolecular Forces Dipole forces attract polar molecules together: the partial negative side attracts to the positive side of the next molecule

Intermolecular Forces Hydrogen bonds are especially strong dipole forces between hydrogen atoms and either oxygen, fluorine, or nitrogen. This is because hydrogen is so small and can get so close to the other atoms. Hydrogen bonds are not actual chemical bonds, just intermolecular forces

Diatomics Diatomic = Molecules that are composed of two of the same element only. Examples: H2, N2, O2, F2, Cl2, Br2, I2, At2