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Department
Chemistry
Course
CHM 103
Professor
Dombi
Semester
Fall

Description
Forces Between Particles Naming Binary Ionic Compounds ● binary ionic compounds are names using the following pattern: ● name = metal name + stem of nonmetal name +-ide ● the stem names and ionic symbols for some common nonmetals are given below: ○ table 4.2 ● ionic compounds are salts Examples of Binary Ionic Compound Names ● Name K 2: ○ name = metal + nonmetal +ide ○ name = potassium + ox- + -ide = potassium oxide ● Name Mg N3 2 ○ finish Naming Binary Ionic Compounds in which metals form ions with more than one charge ● some metal atoms, especially inner and transitional form more than one type of charged ion (e.g. Cobalt forms both Co2+ and Co3+) ● do not need to use roman numerals for representative metals ● binary compounds containing such ions are named following the pattern given earlier with one addition, the number of positive charges on the metal ion is indicated by a roman numeral in () following the metal name ● the roman numerals in the () is a charge Ionic Compound Structure ● the stable form of an ionic compound is not a molecule but a crystal in which many ions of opposite charge occupy lattice sites in a rigid three-dimensional arrangement called a crystal lattice Ionic Compound Formulas and Weights ● formulas for ionic compounds represents only the simplest combining ratio of the ions in the compounds, not the precise numbers of atoms of each element found in a molecule ● Formula Weight is the sum of the atomic weights of the atoms shown in the formula of an ionic compound, this is similar to molecular weight ● one mole of an ionic compound contains avogadro's number of the simplest combine ratio of ions in the compound Covalent Bonding ● covalent bonding is a type of bonding in which the octet rule is satisfied when atoms share valence electrons. the shared electrons are counted in the octet of each atom that shares them as illustrated below for fluorine gas, F2. ● the atoms sharing on or more pairs of electrons are each attracted to the shared electrons, and thus, are attracted to each other, the attraction to each other is called a covalent bond. the covalent bond may be represented by the shared pair or by a single line between the bonded atoms ● covalent bonds are between two nonmetals ● the sharing of electrons takes place when electrons containing orbitals of atoms overlap. this is shown in the formation of the H2 molecule ● electron sharing resulting in covalent bonding can occur between identical atoms or between two different atoms ● Cl2, O2, N2 = two of the same atoms ● H2O, CH4 = different atoms ● there can be lone pairs and single/double/triple bonds Table 4.3 Drawing Lewis Structure with Covalent Molecules ● Step 1 ○ use molecular formula to determine how many atoms of each type are in the molecule ● step 2 ○ use provided connecting pattern of atoms to draw an initial molecular structure with the atoms properly arranged ● Step 3 ○ determine the total number of valence-shell electrons contained in the atoms of the molecule ● Step 4 ○ put one pair of e- between each bonded pair of atoms in the initial structure drawn in step2 ○ subtract the number of e- used in this step from the total number determined in step 3 ○ use the remaining e- to complete the octets of all the other atoms in the structure, beginning with the atoms that are present in greatest number in the molecule ○ remember, hydrogen atoms only require one pair of e- to achieve the electron configuration of helium ● Step 5 ○ if all the octets cannot be satisfied with the available e-, move pairs that are not located between atoms to positions between atoms to complete octets. this will create double or triple bonds between some atoms ● Example: SO 3 ○ Step 1: ■ The formula indicates one S and three O atoms are in the molecule. ○ Step 2: ■ The connecting pattern is that each O is bonded only to the S. Thus, the following arrangement is drawn: ○ Step 3: ■ Sulfur and oxygen are both in group VIA, and so each atom has 6 valence electrons. The total number of electrons is 24 (6 from the one S atom and 18 from the three O atoms). ○ Step 4: ■ One pair of electrons is put between each O atom and the S atom of the arrangement drawn in step 2. ■ This required 6 of the 24 available electrons. The remaining 18 are used to complete the octets of the atoms, beginning with the O atoms. ○ Step 5: ■ After step 4, it is seen that the octet of S is not completed, even though all available electrons have been used. ■ One nonbonding pair from any of the three O atoms will be moved to a location between the O and the S atoms. This pair will continue to count toward the octet of the O, but will also now count toward the octet of the S. ■ The resulting correct Lewis structure contains one double bond (two shared pairs) between the S and one of the O atoms. Naming Covalent Molecules ● Greek Prefixes for covalent bonds ○ mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca ● covalent compounds share electrons ● they do not contain a metal atom ● H2O is water and NH3 if ammonia Polyatomic ions ● Polyatomic ions are covalently-bonded groups of atoms that carry a net electrical charge. Most common polyatomic ions are negatively charged. ● Lewis structures can be drawn for polyatomic ions using the same steps that were shown earlier for covalent molecules with one change. In Step 3, one electron is added to the total for each negative charge found on the polyatomic ion and one electron is subtracted from the total for each positive charge found on the polyatomic ion. All other steps are used unchanged. ● Memorize: ○ sulfate SO42- ○ Nitrate NO - 3 2- ○ Carbonate CO 3 ○ phosphate PO 43- ○ hydroxide OH- ○ Ammonium NH 4+ Shapes of Mo
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