calent bonds form when non-metals share electrons to achieve a stable electron configuration we call these compounds molecules the chemical behavior of these molecules is determined by their shape and polarity in this video we'll learn how to identify the shapes or geometries that molecules form and how to use these geometries to determine a molecule's overall polarity Luis structures show how veence electrons are organized around the atoms within a molecule around the central atom in a structure we called the electrons that are grouped in bonds or lone pairs electron domains for example the central sulfur atom and sulfur dioxide has three electron domains including the double bond lone pair of electrons and single Bond the electrons Within These domains are constantly repelling each other pushing the domains to arrange the M themselves in three-dimensional space to minimize this repulsion and maximize the angle between Each Bond we can analyze a structures electron domains to help predict the shape around the central atom this is called veence shell electron pair repulsion or VPR Vesper Theory to understand Vesper Theory we'll analyze the relationship between a molecule's number of electron domains and its corresponding geometry in bond angles the two descriptions we'll use for a molecule shape are called its electron geometry and molecular geometry electron geometry describes the shape of all electron domains in three-dimensional space however when a molecule is viewed the non-bonding electron pairs aren't visible despite their influence on the structure through the repulsion of the other electron domains the shape formed by just the atoms in the mole molecule is called its molecular geometry let's begin by looking at the leis structures of three molecules that each have four electron domains we have methane ammonia and water while each of these molecules have the same number of veence electrons available for bonding they'll each share their electrons in different ways the carbon and methane for example achieves its octet structure through four bonds whereas the nitrogen and ammonia has three bonds and one non-bonding pair of electrons and the oxygen in water has two bonds and two pairs of non-bonding electrons let's start our investigation with methane this is a good place to begin as methane doesn't contain any non-bonded electron domains because of this its electron geometry and molecular geometry are both described as tetrahedral representing the shape created by all four electron domains in three-dimensional space it's important to note that atoms whose electron domains are all bonded will have the same electron and molecular geometry let's look at ammonia next ammonia replaces one of our four electron domains with a lone pair of electrons notice how the electron geometry remains constant with methane as they have the same total number of domains however the shape of the atoms in the molecule can be described as trigonal pyramidal due to the presence of the lone pair of electrons above nitrogen water replaces another of our four domains with a lone pair of electrons its electron geometry remains constant as tetrahedral as it retains a total of four domains but its molecular geometry can now be identified as bent as the three atoms form an angular line the number of Lone pairs of electrons in a structure will also have an impact on the structures expected Bond angles take a tetrahedral for example the expected Bond angles of a tetrahedral are each 109.5° however when we replace one of our domains with a lone pair of electrons we see a decrease in the measured Bond angle 109.5° decreases to 107 replacing a second domain decreases the bond angle even further from 107° to 104.5 this is because each additional lone pair of electrons will occupy a bit more space than the electrons stored in bonds and as a result will cause an increased repulsion with the bonding electrons that will push the bonds inward decreasing their bond angles we see these Bond angles show up in our structures for methane ammonia and water with water having the smallest Bond angle is it has the most non-bonded pairs of electrons and methane with the largest Bond angles as each of its domains are bonded to further our understanding of molecular geometries let's briefly examine molecules with three electron domains by taking a look at methanal and ozone starting with methanol the central carbon has three electron domains note that the double bond only counts as one electron domain and not two the greatest separation of each of the three domains occurs on a single plane creating Bond angles of 120° and the shape of a flat triangle the electron and molecular geometries for methanol will be the same as there are no lone pairs of electrons these geometries are aptly described as trigonal planer the ozone molecule also has three electron domains and as a result we have a trigonal planer electron geometry as with the tetrahedral molecules of ammonia and water the non-bonding electron pair seen in Ozone does indeed effect its molecular geometry the molecule of ozone appears bent with a bond angle of about 117° slightly less than the expected 120 this is again due to the increased repulsion of the lone pair of electrons on the central oxygen atom we can organize possible molecular geometries into a chart that allows us to see the relationship between electron domains and the number of Lone pairs around a central atom here are the molecular geometry trees for three and four electron domains we also have a row for two electron domains an example of this would be carbon dioxide CO2 carbon dioxide has two domains around its Central carbon atom bester theory tells us that the molecule will appear linear with a bond angle of 180° to achieve maximum separation between the two electron domains molecular geometry will play a large role in a molecule's overall polarity and as a result how it interacts with other compounds within a calent compound it's bonds are classified as polar or non-polar based on their differences and electro negativity polar bonds create partial positive and negative charges called Bond dipoles we could represent these dipoles with an arrow pointed toward the more electronegative element with a notch added to the opposite side of the arroe head noting the partially positive side of the bond while individual bonds can be polar polar bonds don't always cause an entire molecule to have a dipole moment it is instead the presence and orientation of these bonds determined by the molecules geometry that will cause bond dipoles to either cancel each other out or add together let's dive into this by looking at two molecules that have polar bonds but are overall considered to be non-polar to start carbon tetrachloride has four polar bonds its tetrahedral structure points the individual Bond dioles of each carbon to chlorine in opposite directions being pulled with equal force in opposing directions these electron dipoles will cancel each other out making carbon tetrachloride a nonpolar molecule the same is true of carbon dioxide the carbon oxygen bond is also considered polar taking a linear molecular geometry the dipole moments between each carbon to oxygen Bond will pull in opposite directions with equal force these dipoles cancel each other out making carbon dioxide a non-polar molecule now let's take a look at some polar molecules we'll start by replacing one chlorine atom in carbon tet chloride with a hydrogen atom creating Tri chloromethane known commonly as chloroform the carbon hydrogen bond is generally considered to be non-polar due to the small difference in electro negativity between carbon and hydrogen with the lack of a fourth dipole moment the carbon to chlorine dipoles no longer cancel each other out and are tetrahedral shape because electrons are being pulled in one Shar Direction which we can show with an overall molecular dipole in Red Tri chloromethane is considered to be a polar molecule taking another look at methanol the two carbon hydrogen bonds are considered non-polar while the carbon to oxygen bond is considered polar the dipole moment created by the carbon oxygen Bond doesn't cancel out with anything else in the trigonal planer structure this will create an overall dipole moment pointing towards oxygen making methanol a polar molecule finally in ammonia we have polar hydrogen to nitrogen bonds the lone pair of electrons on the central nitrogen atom gives this structure a trigonal pyramidal molecular geometry the movement of the lone pair away from the bonding electrons is further exaggerated by the stronger pull that the n nitrogen has on the bonding electron pairs relative to hydrogen the bond dipoles created by the hydrogen to nitrogen Bond point in and up toward nitrogen the shared upward direction of these dipoles gives ammonia an overall dipole moment making it a polar molecule not only does the nature of calent bonding alter the properties of different substances but variations in calent bonding can alter the properties of the same substance with its four veence electrons carbon can bond in different ways creating different forms of the same element called allotropes the three different allotropes of carbon are graphite diamond and furin each carbon and graphite forms a trigonal planer geometry creating sheets of repeating hexagonal shapes layers of these graphite sheets stack together and are held in place by weak lended dispersion forces graphite is a good conductor of electricity it's very stable and is used in the core of pencils and as a lubricant due to the ability of sheets of graphite to slide past one another in Diamond each carbon atom is bonded to four other carbons in a tetrahedral geometry diamond is considered to be a network calent solid and is the hardest substance known with a very high melting point like graphite the four urine arrangement of carbon atoms is also trigonal with each carbon bonded to three others however the bonding is not quite planer as the structure forms a sphere of 60 carbon atoms resembling a carbon soccer ball for urines are semiconductors and are very light and strong with a low melting point the application for the different allat trps of carbon are widespread varied and ever increasing due to the unique properties of the different calent bonding Arrangements in summary the repulsion between bonded and non-bonded veence electrons in calent structures causes the molecules to take shapes known as their electron in molecular geometry different varieties of shapes within the same element create allotropes within bonds of these molecules electrons can be pulled toward one atom more than another creating Bond dioles if there is a high amount of symmetry in the force and direction of these Bond dioles they can cancel each other out if not they add together in One Direction creating polar molecules with an overall dipole moment learning about the geometry and polarity of calent compounds is vital to understanding the chemical behavior of calent molecules and the intermolecular forces that attract them to each other