The slideshow shows a covalent bond being formed between a hydrogen atom and a chlorine atom, to form hydrogen chloride. A hydrogen atom with one electron and a chlorine atom with 17 electrons. The hydrogen atom has bonded with the chlorine atom, meaning there is now a shared pair of electrons.
After bonding, the chlorine atom is now in contact with eight electrons in its outer shell, so it is stable. The hydrogen atom is now in contact with two electrons in its outer shell, so it is also stable.
Both nuclei are strongly attracted to the shared pair of electrons in the covalent bond, so covalent bonds are very strong and require a lot of energy to break. Hydrogen can be considered to be in Group 1 or Group 17 because it has properties similar to both groups.
Hydrogen can participate in both ionic and covalent bonding. When participating in covalent bonding, hydrogen only needs two electrons to have a full valence shell.
As it has only one electron to start with, it can only make one bond. Hydrogen is shown in Fig 2. In the formation of a covalent hydrogen molecule, therefore, each hydrogen atom forms a single bond, producing a molecule with the formula H 2.
A single bond is defined as one covalent bond, or two shared electrons, between two atoms. A molecule can have multiple single bonds. For example, water, H 2 O, has two single bonds, one between each hydrogen atom and the oxygen atom Fig. Figure 2. Sometimes two covalent bonds are formed between two atoms by each atom sharing two electrons, for a total of four shared electrons. For example, in the formation of the oxygen molecule, each atom of oxygen forms two bonds to the other oxygen atom, producing the molecule O 2.
Similarly, in carbon dioxide CO 2 , two double bonds are formed between the carbon and each of the two oxygen atoms Fig. In some cases, three covalent bonds can be formed between two atoms. The most common gas in the atmosphere, nitrogen, is made of two nitrogen atoms bonded by a triple bond.
Each nitrogen atom is able to share three electrons for a total of six shared electrons in the N 2 molecule Fig. In addition to elemental ions, there are polyatomic ions. Polyatomic ions are ions that are made up of two or more atoms held together by covalent bonds. Polyatomic ions can join with other polyatomic ions or elemental ions to form ionic compounds. It is not easy to predict the name or charge of a polyatomic ion by looking at the formula.
Polyatomic ions found in seawater are given in Table 2. Polyatomic ions bond with other ions in the same way that elemental ions bond, with electrostatic forces caused by oppositely charged ions holding the ions together in an ionic compound bond. Charges must still be balanced. For example, in Fig. In Figure 2. P olyatomic ions can bond with monatomic ions or with other polyatomic ions to form compounds. In order to form neutral compounds, the total charges must be balanced. A molecule or compound is made when two or more atoms form a chemical bond that links them together.
As we have seen, there are two types of bonds: ionic bonds and covalent bonds. In an ionic bond, the atoms are bound together by the electrostatic forces in the attraction between ions of opposite charge.
Ionic bonds usually occur between metal and nonmetal ions. For example, sodium Na , a metal, and chloride Cl , a nonmetal, form an ionic bond to make NaCl. In a covalent bond, the atoms bond by sharing electrons. Covalent bonds usually occur between nonmetals. For example, in water H 2 O each hydrogen H and oxygen O share a pair of electrons to make a molecule of two hydrogen atoms single bonded to a single oxygen atom. In general, ionic bonds occur between elements that are far apart on the periodic table.
Covalent bonds occur between elements that are close together on the periodic table. The hydrogen atom has bonded with the chlorine atom, meaning there is now a shared pair of electrons. Most covalently bonded substances consist of small molecules. A molecule is a group of two or more atoms joined together by covalent bonds. Molecules of the same element or compound always contain the same number of atoms of each element.
The atoms in a molecule are always joined together by a covalent bond. Substances that are made up of ions do not form molecules. A small molecule contains only a few atoms, so atoms and small molecules have a similar range of sizes.
They are very small, typically around 0. Individual atoms and molecules are too small to see even with the most powerful light microscope. Some electron microscopes can produce images of atoms and simple molecules.
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