The\nsize of molecule is greater than atoms. The size is depend upon number of atoms\npresent and their shapes. Some molecules are so large so they are called\nmacromolecules like Haemoglobin present in blood. It helps to carry oxygen from\nlungs to all parts of our body. Each molecule is made up of approximately\n10,000 atoms and it is 68,000 times heavier than hydrogen.<\/p>\n\n\n\n
Types of molecules <\/h2>\n\n\n\n
On\nthe structural point of view a molecule is consist of atoms which are held\ntogether through valence force. There are different types of molecules:<\/p>\n\n\n\n
Diatomic molecule:<\/h3>\n\n\n\n
The\nmolecules which contain two atoms and chemically bonded with each other. If the\ntwo atoms are same or identical like oxygen O2<\/sub> they known as\nhomonuclear diatomic molecule, but if the atoms are not identical like carbon\nmonoxide CO then they called as heteronuclear diatomic molecule.<\/p>\n\n\n\n The\nmolecules which contain more than two atoms are called as polyatomic molecules.\nFor example carbon dioxide CO2<\/sub>.<\/p>\n\n\n\n It\nis large molecule like protein, made by polymerization of smaller subunits.\nThey are consists of thousands of atoms or more. <\/p>\n\n\n\n Physical\nproperties of molecules are depend upon intermolecular forces of attraction.\nThese are the following properties:<\/p>\n\n\n\n 1. Melting and boiling points<\/strong><\/p>\n\n\n\n Molecular\ncompounds like liquid and gases have low melting and boiling point because\ntheir atoms are bonded by covalent bond which can separate from each other when\nsmall amount of energy is applied to them. Melting and boiling point is depend\nupon the strength of intermolecular forces. Large molecules have more van der\nWaals force of attraction so they required more energy to break [2].<\/p>\n\n\n\n 2. Solubility<\/strong><\/p>\n\n\n\n Molecular\ncompounds are insoluble or sometime sparingly soluble in water, they usually\nreact and form hydrogen bonds with them. Methane is soluble in water because it\nis a gas and weaker van der Waals forces so small amount of energy is evolved\nas resultant. Ammonia has also ability to make hydrogen bonds. When ammonia\nreacts with water it form ammonium ions and hydroxide ions. The substances\nwhich are readily dissolve in water are ethanol and sucrose. Some molecular\ncompounds are soluble in organic solvent. Both solute and solvent are attracted\neach other by van der Waals forces.<\/p>\n\n\n\n 3. Electrical conductivity <\/strong><\/p>\n\n\n\n Molecular\ncompounds are not dissociate into ions but dissolve into molecules so they\ndon\u2019t conduct electricity [3]. Electrons are delocalized within molecule, there\nis not sufficient connection between molecules are electron which allow them to\nmove freely in the whole solid or liquid. <\/p>\n\n\n\n The\nstructural chemistry of the molecules is related with the valence shell of\nelectrons, it determines how atoms combine together in proper ratios. It is\nalso related to the bond type, direction and its length. The properties are\nrelated with the structure like water has hydrogen bonding and has bent\nstructure, however carbon dioxide has no dipole moment that\u2019s why it has linear\nstructure. But some molecules like ethane (H3<\/sub>CCH3<\/sub>) have\nfree rotation around carbon carbon single bond, they may not be rigid in\nstructure [4]. <\/p>\n\n\n\n In\na molecule the position of nucleus is determined through microwave vibration\nrotation spectra or by neutron diffraction. Molecular structure is find\ntheoretically through solving the quantum mechanical equation for the motion of\nelectrons. Numerically it can be find out through Schr\u020ddinger equation, which\nis highly developed process use of computers and supercomputers.<\/p>\n\n\n\n VSPER (Valence shell electron pair repulsion) theory determined the geometry of molecules and also electron group geometry. This theory defines that electron pairs repel each other either they are in bond pair or lone pair, that\u2019s why electron pairs spread themselves to repulsion. It also focus on the electron group which can be a double bond or triple bond on the center atom, an electron pair, a single pair. Through bond pair VSPER theory predict the shape of a molecule.<\/p>\n\n\n\n The shape of molecule is predict by the location of nuclei and its electron. They minimize repulsion and increase attraction. So molecule\u2019s shape show its equilibrium state. It also predict the distribution of electron. It is also depend upon spatial orientation of covalent bonds to atoms and having two or more bonding partners. Configuration of molecule is three dimensional. The bonding of carbon is very easy to remember O=C=O.<\/p>\n\n\n\n A molecule which has one or more covalent bonds which are polar so they have dipole moment due to accumulation of bond dipoles. In O-H covalent bond is polar due to difference in electronegativity of oxygen and hydrogen. <\/p>\n\n\n\n The molecular weight is sum of atomic weights of its component, molecular weight is termed as mole. It can be determined by mass spectrometry and some techniques which are based on thermodynamics or kinetic transport phenomena.<\/p>\n\n\n\n Iodine (I2<\/sub>)<\/strong><\/p>\n\n\n\n It\nis dark grey crystalline solid. Its melting point is 114o<\/sup>C and\nboiling point is 184o<\/sup>C. Iodine is very slightly soluble in water but\neasily dissolve in organic solvent. Its structure is defined as face centered\ncubic, at the center of each face another iodine molecule is attached. The\norientation with the structure is very difficult to draw. The distance between\nthe centers of atom in the crystal show two different values, the atoms which\nare at shorter distance have covalent bond and those which are at larger\ndistance have van der Waals force of attraction, much weaker as compare to\nother force of attraction.<\/p>\n\n\n\n Ice <\/strong><\/p>\n\n\n\n Ice\nmolecules can be arranged in different ways, it is good example of hydrogen\nbonded solid. Huge number of molecules are arranged in three dimension. In the\ndiagram hydrogen bonding is represented by straight lines and lone pairs are\nattached at the left side. Ice in cubic form stable at temperature below -80o\n<\/sup>C. The ice in hexagonal structure called \u201cice lh\u201d. There is large amount\nof empty space present in between molecules in the structure, so when ice melts\nmolecules fit in the empty spaces. Most of the solid will increase in volume on\nmelting but ice has very unusual behavior in this respect. The opposite\nsituation happened when water freezes hydrogen bonded structure is expanded but\nliquid contract on freezing.<\/p>\n\n\n\n Density of water increases from 0o<\/sup>C to 4o<\/sup>C molecules are free themselves from open structure and occupy less space. But after 4o<\/sup>C density fall because of the motion of molecules [5]. <\/p>\n\n\n\n Bonding in polymers<\/strong><\/p>\n\n\n\n Polymers\nconsist of very long chain molecules like poly(ethene) which is also called\npolythene. These are made up of long chain of ethane molecules in which\nhydrogen and carbon atoms are covalently bounded. Along with main chain short\nbranches are also present, carbon chain with attached hydrogen are also present.<\/p>\n\n\n\n It\nalso contain two more distinct branches by controlling the conditions in which\nethane is polymerized.<\/p>\n\n\n\n High Density polythene<\/strong><\/p>\n\n\n\n It\nhas very few branches, that\u2019s why molecules lie very close to each other just\nlike crystal. Lack of branches make plastic very strong because dispersion\nforce is strong. It has also high melting point as compare to low density\npolythene.<\/p>\n\n\n\n It\nis also used for household chemicals like washing up liquid, for bowls and\nbucket preparation.<\/p>\n\n\n\n Low density polythene<\/strong><\/p>\n\n\n\n It\nhas many branches along the chain. That\u2019s why molecules are not lie close\ntogether. It makes very low quality plastic. Molecules are not in a tidy manner\nalso make dispersion force less effective. It also has low melting point and\ndensity.<\/p>\n\n\n\n It\nis used for the preparation of plastic bags.<\/p>\n\n\n\n Molecule Definition A molecule is the smallest particle of a pure substance which can exist independently. It can be divided but retain its composition and chemical properties of that substance. When atoms combine by forming covalent bonds then the collection of atoms are called molecule. It is also called as simplest unit of covalent compound … Read more<\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"rating_form_position":"","rating_results_position":"","mr_structured_data_type":""},"categories":[1],"tags":[],"multi-rating":{"mr_rating_results":[{"adjusted_star_result":5,"star_result":5,"total_max_option_value":5,"adjusted_score_result":5,"score_result":5,"percentage_result":100,"adjusted_percentage_result":100,"count":1,"post_id":1132}]},"_links":{"self":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/1132"}],"collection":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/comments?post=1132"}],"version-history":[{"count":5,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/1132\/revisions"}],"predecessor-version":[{"id":1321,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/1132\/revisions\/1321"}],"wp:attachment":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/media?parent=1132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/categories?post=1132"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/tags?post=1132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Polyatomic molecule<\/h3>\n\n\n\n
Macromolecule<\/h3>\n\n\n\n
Properties <\/h3>\n\n\n\n
Structure of Molecules<\/h2>\n\n\n\n
![\"\"](\"https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/11\/image-13.png\" "\\"\\"")
<\/figure>\n\n\n\nSome individual examples <\/h2>\n\n\n\n
Polymers <\/h2>\n\n\n\n
Reference <\/h4>\n\n\n\n