Problem: Article: When two atoms are bonded together, the difference between their electronegativities can tell you about the qualities of their bond. Subtract the smaller electronegativity from the larger one to find the difference. For example, if we're looking at the molecule HF, we would subtract the electronegativity of hydrogen (2.1) from fluorine (4.0). 4.0 - 2.1 = 1.9 Here, the electrons are shared almost equally. These bonds don't form molecules that have large charge differences on either end. Nonpolar bonds tend to be very difficult to break. This is because the atoms are sharing electrons, making their bond stable. It requires a lot of energy to break this bond. For example, the molecule O2 has this type of bond. Since the two oxygen's  have the same electronegativity, the difference between them is 0. These bonds have more of the electrons at one end than the other. This makes the molecule a little more negative at the end with the electrons and a little more positive at the end without them. The charge imbalance in these bonds can allow the molecule to participate in certain special reactions, such as joining with another atom or molecule or pulling a molecule apart. This is because it's still reactive. A good example of this is the molecule H2O (water). The O is more electronegative than the two Hs, so it holds the electrons more tightly and makes the entire molecule partially negative at the O end and partially positive at the H ends. In these bonds, the electrons are completely at one end of the bond. The more electronegative atom gains a negative charge and the less electronegative atom gains a positive charge. These sorts of bonds allow their atoms to react well with other atoms and even be pulled apart by polar molecules.  An example of this is NaCl (sodium chloride or salt). The chlorine is so electronegative that it pulls both electrons in the bond all the way towards itself, leaving sodium with a positive charge. NaCl can be broken apart by a polar molecule, such as H2O (water). In a water molecule, the hydrogen side of the molecule is positive, while the oxygen side is negative. When you mix the salt into the water, the water molecules break down the salt molecules, dissolving the salt. If there is a metal in the bond, the bond is ionic. If there are only non-metals, the bond is polar covalent.  Metals include most of the atoms on the left side and the middle of the periodic table. This page has a table that shows which elements are metals.  Our HF example from above falls in this range. Since H and F aren't metals, they have a polar covalent bond.
Summary: Find the electronegativity difference between the two atoms. If the difference is below about 0.5, the bond is nonpolar covalent. If the difference is between 0.5-1.6, the bond is polar covalent. If the difference is over 2.0, the bond is ionic. If the difference is between 1.6-2.0, check for a metal.

Problem: Article: Finding out what your face and body shapes are will help you to match these to the ideal dress, one that flatters and accentuates all of your good features, hiding anything you might consider a flaw. The steps in this section will help you to match your face and body shapes to your dress style. This means that you can choose any type of neckline you like.  If you have a round face (as wide as it is long, a little narrower at the forehead and jawline), you should look for a prom dress that elongates your face to make her look more oval. V-necks, Queen Anne and Empire necklines, sweetheart and scoop necks suit best your oval face. Always avoid high neck dresses and supersized necklaces, as they tend to hide the neck and therefore make your face look even more round. If you have a triangle face (wide jaw line, narrow forehead), look for necklines with a stronger vertical shape that can add curves to your face: Sabrina necklines, scoop necks, sweetheart necklines and cowl necks. If you have a heart shaped face (sharp and oval chin, slightly prominent cheekbones, wide forehead), you need to make your face look wider, so opt for necklines that draw a horizontal line near the neck: high or wide necklines. If you have a square face (square jaw line, forehead, cheekbones and jaw having the same width), the perfect prom dress for you should have a vertical shape, so look for scoop necks, Sabrina, sweetheart, cowl neck styles, and always avoid square necklines. If you have an oblong face (prominent chin, forehead, cheekbones and jawline having the same width), look for prom dresses with necklines that can make your face look wider and more oval: round, wide, Sabrina and cowl necks. Also, stay away from V-neckline dresses. You could be an apple, pear, hourglass, vase. There are various different categories for body shape and you can find your body shape by reading: How to determine your body shape. To match the body shape and dress, here are some suggestions:  If you have an hourglass body shape (well-defined waist, torso and hips having about the same width), look for prom dresses that accentuate the waist and keep a perfect balance between tops and bottoms: if they have sleeves, a full skirt is required; if the top of the dress is tight, the skirt must also tightly follow the hips and thighs. If you have a rectangle body shape (no defined waistline, shoulders, bust and hips having the same width), you need to define your waist and add volume on both your upper and lower body. The best prom dresses for you are draped dresses with a defined waist and full skirt, Empire dresses, A-lines and any dress with a full skirt, ruffles and folds. If you have an inverted triangle body shape (little waist definition, shoulders and bust larger than the hips), you must add volume to your lower body in order to draw attention away from your broad shoulders. You can create the hourglass silhouette illusion by wearing Empire line dresses, A-lines with deep V-necks, wrap dresses with a higher waist and other dresses with full skirts and details or embellishment on the hips. If you have a pear body shape (torso and upper body smaller than the hips), you must make your silhouette look like the ideal hourglass figure, so look for prom dresses that draw attention to your shoulders and bust and reduce your lower body: A-line dresses, wrap and draped bust dresses, as well as prom dresses with well-defined waist and embellishments that draw attention to your upper body. If you have an apple body shape (little or no waist definition, upper body wider than the hips), you need dresses that can create the illusion of a slimmer waist while keeping the right balance between the upper and lower body: Empire and A-line dresses with simple tops and a low and wide neckline (scoop, square, sweetheart).
Summary:
Focus on matching the dress to your face and body shapes, to ensure the ideal look and fit, therefore making your job of finding a dress easier. Consider your face shape in order to choose the perfect neckline If you have an oval face, then you are blessed with what it is considered to be the ideal face shape - forehead wider than the chin, cheekbones slightly prominent and face delicately narrowing towards the chin, which is narrow and oval. Know your body shape and how to match it to the perfect cut.