Firstly, a covalent bond results when two atoms "share" valence electrons between them.
• Covalent compounds consist of molecules and not ions. The molecules do not have any electric charge on them. The molecules are held together by weak forces called Van der Waal's forces.
• Covalent compounds are either gases, volatile liquids or soft solids. As there are weak, Van der Waal's forces between the molecules, they are not held in rigid position. The state depends on the bond energy. If the bond energy is very low, they stay as gases, if it is appreciable they are volatile liquids. If very high, they exist as soft solids.
• Covalent compounds generally have low melting and boiling points. As Van der Waal's forces are weak, a very small amount of energy is required to break the bond between the molecules corresponding to low melting point and boiling point.
• Covalent compounds dissolve in organic solvents. As they do not contain ions, solvation does not take place when water is added to the compound. Hence they do not dissolve in water.
• Covalent compounds are bad conductors of electricity. They do not contain ions in the fused state, nor do ions migrate on application of an electric potential. Hence, there is no conduction of current.
• Covalent compounds are less dense when compared to water. Very weak Van der Waal's forces hold the molecules together, hence there are large inter molecular spaces. Consequently less number of molecules per unit volume, which means mass per unit volume is also less. Hence they have a low density.
A good example of a covalent bond is that which occurs between two hydrogen atoms. Atoms of hydrogen (H) have one valence electron in their first electron shell. Since the capacity of this shell is two electrons, each hydrogen atom will "want" to pick up a second electron. In an effort to pick up a second electron, hydrogen atoms will react with nearby hydrogen (H) atoms to form the compound H2. Because the hydrogen compound is a combination of equally matched atoms, the atoms will share each other's single electron, forming one covalent bond.
Exceptions:
Diamond and graphite, the allotropes of carbon have high melting point.
Hydrogen chloride in the aqueous state conducts electricity.
Glucose, sugar and urea are soluble in water. Ammonia and hydrogen chloride also dissolve in water.
Secondly, ionic bonding is nothing but a type of chemical bond formation. Ionic bonding is the process of formation of a chemical bond by complete transfer of electrons from one atom to another. When the atoms lose or gain electrons, they become differentially charged ions or oppositely charged ions. The charged ions are then attracted towards each other due to the resulting electrostatic force. The electrostatic force gives rise to the formation of an ionic bond. The most common example of ionic bonding is the formation of sodium chloride in which the sodium atom donates its outer electron to the chlorine atom, which required only one electron to fill its outer shell. The sodium ion becomes positively charged due to the loss of electron whereas the chloride ion becomes negatively charged due to the addition of the electron. The oppositely charged ions thus are attracted to each other and result in the formation of an ionic bond.
• Owing to the fact that metals tend to lose electrons and non-metals tend to gain electrons, ionic bonding is seen between metals and non-metals. Hence unlike covalent bonds, ionic bonds can be formed between metals and non-metals.
• While naming the ionic compounds the name of the metal always comes first and the name of the non-metal comes second. For instance in case of common salt that is chemically named sodium chloride. Sodium is the metal whereas chlorine is the non-metal.
• Compounds which contain ionic bonds dissolve quickly in water as well as several other polar solvents. Ionic bonds thus tend to have an effect on the solubility of the resultant compounds.
• When ionic compounds are dissolved into a solvent to form a homogeneous solution, the solutions tends to conduct electricity.
• Ionic bonding has an effect on the melting point of the compounds as well. Ionic compounds have higher melting temperature, which means that ionic bonds remain stable for a greater temperature range.
Ionic bonds normally form crystalline atoms and have higher melting points and boiling points compared to covalent compounds. These conduct electricity in molten or solution state and they are extremely polar bonds. Most of them are soluble in water but insoluble in non-polar solvents. They require much more energy than covalent bond to break the bond between them.
There is a third type of bonding, called metallic bonding. As the name implies, metallic bonding usually occurs in metals.
According to Electron sea model or Electron gas theory, a metallic bond can be defined as a force of attraction that holds firmly a definite geometrical arrangement of metal ions and sea of freely moving electrons. The force of attraction between a group of electrons and a group of positive ions should be stronger when compared to the force of attraction between one electron and one nucleus. The metallic bond is non-directional. Metallic bond is weaker than a covalent bond.
• The metal atoms lose their valence electrons readily. They can form a group of positively charged ions called Kernel.
• The positively charged metal ions are arranged in a definite geometric shape. This array or kernel of metal ions is submerged in the sea of freely moving electrons.
• Due to smaller ionization energy, the valence electrons of metal are not held by the nucleus firmly and the electrons can move freely using vacant orbitals.
• The mobile electrons move around the group of metal ions freely similar to the free movement of sea water or any gas. Hence, it is called electron sea model for metallic bond formation or electron gas theory.
• Metallic bond is formed by mutual attraction between mobile electrons and positive metal ion layers.
• Metallic bond is weaker because valence electrons are mobile and weakly attracted by metal ions.
• Bond is present around identical metal ions.
• Metallic bond is weaker because mobile electrons are weakly attracted by metal ions.
The strength of metallic bond formation depends on:
• Number of valence electrons.
• Charge on the metal ions.
• Size of the metal ions.
Metallic bond is weaker in alkali metals because of:
• Only one valence electron on each metal atom.
• One positive charge on the metal ion.
• Larger size of the metal ion.
Transition metals have a strong metallic bond because:
• The number of valence electrons are more
• Metal ions have higher positive charges.
• Smaller size of these metal ions.
Any metal you hold in your hand is held together with flexible metallic bonds. These bonds are what enable metal to be both malleable and ductile.
Essential to understanding all types of chemical bonding is realizing that all bonds use electron "glue." Every substance is made up of atoms, and all atoms are surrounded by the charged particles called electrons.
Monday, October 25, 2010
Blog Test Question #3
Ionic, Covalent, and Metallic are the three divisions of bonds.
Ionic Bonding
Description: Ionic bonding is when you have a cation (loses an electron to become positively charged) and anion (gains an electron to become negatively charged) combine together due to opposites attracting. This is basically a strong bond between a metal and a non-metal. Also called extrovalent bonding.
Characteristics: Have High melting points. Have Conduct electricity. Dissolve easily in water. Have well-defined crystals. One atom has a high electronegativity value, while the other value is relatively low.
Reasons: The strong bond of metal and non-metal causes a tighter structure and a higher melting point.
Examples: Sodium chloride
Covalent Bonding
Description: A bond formed by the sharing of electrons between atoms and sometimes other covalent bonds. Different types are metal to metal bonding, σ-bonding, and π-bonding. Covalent bonds are affected by the electro negativity of the connected atoms. Two atoms with equal electro negativity will make non-polar covalent bonds such as H-H. An unequal relationship creates a polar covalent bond such as with H-Cl.
Characteristics: Covalent bonds are molecules (neutral). Does not always conduct electricity. Low melting and boiling points. Definite shape.
Reasons: The sturdy “inputs” of the bond can cause the definite shape.
Examples: Hydrogen Chloride
Metallic Bonding
Description: Although the term metallic bond is often used in contrast to the term covalent bond, it is preferable to use the term metallic bonding, because this type of bonding is collective in nature and a single metallic bond does not exist. It is not considered covalent due to some bonds being metal to metal, but not metallic. Based on the sharing of free electrons.
Characteristics: Conductors of heat and electricity. Some of the same characteristics as covalent.
Reasons: The metal on metal causes the heat and electricity conducting.
Examples: Bronze. Brass. Steel.
There are three main types of chemical bonding; covalent, metallic, and ionic.
Covalent bonding, either polar or nonpolar, involves the sharing of a pair of valence electrons by two atoms. The electron pair interacts with the nuclei of both of the atoms, holding them together. A covalent bond is similar in strenght or stronger than the ionic bond and much stronger than the hydrogen bond if it is between polar molecules.
Metallic bonding is when mobile valence electrons are shared among atoms in a usually stable crystalling structure. A more stable configuration is usually achieved. It gets its name because metals usually have the characteristic of valence electrons being not tightly bound with the nucleus. This type of bonding allows each atom in a metal crystal to contribute all of the electrons in its valence shell to all of the other atoms in the crystal.
Ionic bonding is chemical bond that is achieved by the complete transfer of electrons from one atom to another. Typically it involves a metal and a nonmetal ion and the bond is formed by the attraction between the two oppositely charged ions. Sodium Chloride is a common example of an ionic bond. When sodium and chlorine are combined, sodium atoms lose an electron and chlorine atoms gain an electron.
Covalent bonding, either polar or nonpolar, involves the sharing of a pair of valence electrons by two atoms. The electron pair interacts with the nuclei of both of the atoms, holding them together. A covalent bond is similar in strenght or stronger than the ionic bond and much stronger than the hydrogen bond if it is between polar molecules.
Metallic bonding is when mobile valence electrons are shared among atoms in a usually stable crystalling structure. A more stable configuration is usually achieved. It gets its name because metals usually have the characteristic of valence electrons being not tightly bound with the nucleus. This type of bonding allows each atom in a metal crystal to contribute all of the electrons in its valence shell to all of the other atoms in the crystal.
Ionic bonding is chemical bond that is achieved by the complete transfer of electrons from one atom to another. Typically it involves a metal and a nonmetal ion and the bond is formed by the attraction between the two oppositely charged ions. Sodium Chloride is a common example of an ionic bond. When sodium and chlorine are combined, sodium atoms lose an electron and chlorine atoms gain an electron.
Blog #3; Hannah Boynton
There are three divisions for the types of bonds that occur;
-metallic bonding; Metals tend to have high melting points and boiling points suggesting strong bonds between the atoms. The nature of metals in metallic bonding is that they have loosely held electrons that can be taken away easily. Metallic bonding is usually done when metals naturally bond with other metal atoms. About 80 of the 100 elements, are in fact, metals. They are very malleable and ductile. They are very conductive toward heat and electricity. They easily lose electrons during the bonding process.
*Examples; Silver, Copper, Gold.
-ionic bonding; Electrons are completely transferred from one atom to another. In the process of the atoms losing or gaining negatively charged electrons, the reacting atoms form ions. The opposite charged ions are attracted to each other by electrostatic forces, which are the basis of the ionic bond. Ionic bonds form between metals and nonmetals. In naming ionic compounds, the metal always comes first, the nonmetal second. (Ex. Sodium Chloride.) Very soluble in water and other polar solvents. They, also like metals, conduct electricity very easily. Ionic compounds tend to form crystalline solids.
*Example; Sodium Chloride
-covalent bonding; Occurs because the atoms in the compound have a similar tendency for electrons (generally to gain electrons.) Form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, and other covalent bonds. Covalent bonds are usually formed between two atoms that are able to share electrons and are usually gases and are both nonmetals. Covalent is usually found in elements and compounds; unlike the others, it has very low boiling point, low polarity, and has definite shape.
*Example; Hydro Chloric Acid, Methane
-metallic bonding; Metals tend to have high melting points and boiling points suggesting strong bonds between the atoms. The nature of metals in metallic bonding is that they have loosely held electrons that can be taken away easily. Metallic bonding is usually done when metals naturally bond with other metal atoms. About 80 of the 100 elements, are in fact, metals. They are very malleable and ductile. They are very conductive toward heat and electricity. They easily lose electrons during the bonding process.
*Examples; Silver, Copper, Gold.
-ionic bonding; Electrons are completely transferred from one atom to another. In the process of the atoms losing or gaining negatively charged electrons, the reacting atoms form ions. The opposite charged ions are attracted to each other by electrostatic forces, which are the basis of the ionic bond. Ionic bonds form between metals and nonmetals. In naming ionic compounds, the metal always comes first, the nonmetal second. (Ex. Sodium Chloride.) Very soluble in water and other polar solvents. They, also like metals, conduct electricity very easily. Ionic compounds tend to form crystalline solids.
*Example; Sodium Chloride
-covalent bonding; Occurs because the atoms in the compound have a similar tendency for electrons (generally to gain electrons.) Form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, and other covalent bonds. Covalent bonds are usually formed between two atoms that are able to share electrons and are usually gases and are both nonmetals. Covalent is usually found in elements and compounds; unlike the others, it has very low boiling point, low polarity, and has definite shape.
*Example; Hydro Chloric Acid, Methane
Sunday, October 24, 2010
Gabby H.
Ionic Bond
Bond formed by the attraction of two oppositely charged ions
Usually between metals have a positive charge when they bond because they give up electrons and non-metals have a negative charge as they obtain more electrons when bonding
Electrostatic forces (slow moving charges)
anions-negative charge(non-metals)
cations-positive charge(metals)
High melting points, dissolvable in water, conductors, high strength (these characteristics are alike the metallic bond characteristics because both bonds are strong)
Examples: salt-sodium chloride (NaCl), calcium carbonate (CaCO3), baking soda-sodium bicarbonate(NaC2)
Covalent Bond
Bond formed by the sharing of one or more electrons
Usually between two non-metals
Caused by van der Waals forces which are also used in ionic bonds
Low melting point, non-soluble in water, don’t conduct electricity, molecules, weaker bonds than ionic compounds and very often have a stronger scent (caused by weak bonds)
Examples: menthol (C10H20O), water (H20), ammonia (NH3), methane (CH4)
Metallic Bond
Between mobile electrons and fixed positive electrons
Two metals
High conductivity, malleability, luster, high melting points, strength
Electromagnetic forces
Examples: copper, sodium, zinc, lithium, magnesium, iron, calcium,
The three divisions for the types of bonds are: Ionic, Covalent, and Metallic bonds.
1. Metallic Bonding- Metallic bonding is when metal atoms bond with other metal atoms naturally. Metals are the most numerous elements. Metals have substance and aren't easily torn apart. They are ductile and malleable. This means they can be drawn into shapes like, wire for paper clips. They conduct heat and electricity. They can be mixed to form alloys. They also lose electrons when bonding.
2. Ionic Bonding- Ionic bonding is when you have a cation (metal that loses an electron and becomes positively charged) and anion (a non-metal that gains an electron and becomes negatively charged) combine together because they are attracted to each other. They have high melting points. They dissolve easily in water. They can conduct electricity.
Examples: Sodium Chloride,
3. Covalent Bonding- The covalent bond is formed when two atoms are able to share electrons usually gases and are both nonmetals. Covalent bonding is found in elements and compounds. It is essentially found in any material in which a nonmetallic atoms are bonded together. Usually gases. Low boiling point. Low polarity. Has definite shape.
Examples: Methane, Hydro Chloric acid
ASHLEY!
Ionic, Covalent and Metallic bonds are the three divisions of bonds that occur. The ionic bond is the complete transference of electrons from one atom to another. In the process of either losing or gaining negatively charged electrons, the reacting atoms form ions. One atom will be nonmetal and one will be metal;therefore, one will have a low electronegativity value while the other has high. Ionic bonds have very high melting points, they dissolve easily in water, well defined crystals and can conduct electricity. Examples include: NaCl, CaCO3. Covalent Bonds happen when a pair of electrons are shared between atoms in a molecule. A metal plus a nonmetal can form a Covalent bond. Characteristics in a covalent bond are: definite shape, low boiling point, and a low polarity. Some examples are HCl H2,and SO2. Metallic bonds are the electromagnetic interaction between delocalized electrons, and the metallic nuclei within metals. Metallic bonds have many physical properties of metals such as a high electrical conductivity, luster and malleability. Some examples are gold, silver and mercurous ion.
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