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# REVIEWER IN SCIENCE 9 ## Paramagnetic elements Paramagnetic elements are elements that have unpaired electrons. They are attracted to an external magnetic field. An example of a paramagnetic element is 15P. Erwin Schrödinger proposed the probability that electrons will be found in certain locat...

# REVIEWER IN SCIENCE 9 ## Paramagnetic elements Paramagnetic elements are elements that have unpaired electrons. They are attracted to an external magnetic field. An example of a paramagnetic element is 15P. Erwin Schrödinger proposed the probability that electrons will be found in certain locations around the nucleus of an atom. ## Electron configuration Electron configuration is the distribution of electrons in various energy levels. **Take note:** * If *n* = 3, *l*= 1, 2, the 3 energy level *d* sublevel = 3d * If Gallium 31 belongs to the 4th energy level, it belongs to group 3 in the periodic table. ## Chemical Bond Atoms react with each other to form chemical bonds in order to attain stability. * **Ionic bonding**: Occurs when a metal transfers an electron to a non-metal. For example, sodium transfers an electron to a non-metallic element like fluorine. * **Covalent bonding**: Occurs when atoms share electrons with each other. **Examples of Ionic Compounds:** | Compound | Type | |---|---| | AlCl₃ | Ionic | | CH₄ | Covalent | | MgBr₂ | Ionic | | NaCl | Ionic | **Take note:** * Helium (He) does not combine with another He atom to form He₂ because the valence shell of He is completely filled with electrons. * The bond in Br₂ is covalent (both nonmetals), while the bond in MgF₂ is ionic (metal and nonmetal). * A sodium atom and a fluorine atom combine by electron transfer. This is an ionic bond since Na (metal) loses electrons and F (nonmetal) gains electrons. **In general:** Metal atoms lose electrons, forming positive ions. Nonmetal atoms gain electrons, forming negative ions. ## Naming Compounds | Compound | Name | |---|---| | NaCl | Sodium Chloride (Salt) | | NaHCO₃ | Sodium Bicarbonate (Baking Soda) | | AlCl₃ | Aluminum Chloride | | MgO | Magnesium Oxide | | CaF₂ | Calcium Fluoride | ## Carbon and Hydrocarbons * Carbon atoms can form many different organic compounds because they can form many types of bonds with other carbon atoms. * Hydrocarbons contain at least one carbon-carbon triple bond. Alkynes are an example of this; an example is Ethyne. * The maximum number of bonds a carbon atom can form is four (4). * Diamond and graphite are allotropes of carbon. * Diamond is extremely hard and colorless. * Graphite is a very soft, gray substance. * Diamond is used as a cutting tool and in jewelry.