Formulas writing

Write formulas (including charges) of all complex ions formed by cobalt(III) with the hydroxide ion and/or ethylenediamine (eri) molecules as ligands. 

Recalling the chemistry of nitrogen, write formulas for phosphorus compounds corresponding to... 

Name and write formulas for d-metal complexes (Toolbox 16.1 and Example 16.1). 

Atoms and their symbols were introduced in Chap. 3 and 1. In this chapter, the representation of compounds by their formulas will be developed. The formula for a compound (Sec. 4.3) contains much information of use to the chemist. We will learn how to calculate the number of atoms of each element in a formula unit of a compound. Since atoms are so tiny, we will learn to use large groups of atoms—moles of atoms—to ease our calculations. We will learn to calculate the percent by mass of each element in the compound. We will learn how to calculate the simplest formula from percent composition data, and to calculate molecular formulas from simplest formulas and molecular weights. The procedure for writing formulas from names or from knowledge of the elements involved will be presented in Chaps. 5. ft. and 13. 

In Chap. 4 we learned to write formulas and interpret formulas for compounds, and to calculate formulas from experimental data. In this chapter, we learn why compounds have the formulas they have for example, why sodium chloride is NaCl and not NaC 2. 

Write formulas for the compounds formed by the following pairs of ions (a) Na and Cl, ... 

Write formulas for the compounds formed by the reaction of (a) sodium and sulfur, (b) barium and bromine, (c) aluminum and oxygen, (d) lithium and nitrogen, (e) magnesium and nitrogen, (/) aluminum and fluorine, and (g) magnesium and sulfur. 

The first compounds to be discussed will be compounds of two nonmetals. These binary compounds are named with the element to the left or below in the periodic table named first. The other element is then named, with its ending changed to -ide and a prefix added to denote the number of atoms of that element present. If one of the elements is to the left and the other below, the one to the left is named first unless that element is oxygen or fluorine, in which case it is named last. The same order of elements is used in writing formulas for these compounds. (The element with the lower electronegativity is usually named first refer to Table 5-1.) The prefixes are presented in Table 6-2. The first six prefixes are the most important to memorize. 

EXAMPLE 6.8. Write formulas for (a) copper(I) oxide and (b) copper(II) oxide. 

Note that not all the possible oxyanions of these elements exist. If the name and formula are not given in Table 6-5, the ion is not known. If you learn the seven ions that end in -ate plus the meaning of the ending -ite and the prefixes, you will be able to write formulas for 20 oxyanions. You may double this number of names by learning an additional rule in Sec. 6.4. Note from Table 6-5 that for each central element, all ions present have the same charge. 

EXAMPLE 6.16. Write formulas for the following acids (a) nitric acid, (b) hydroiodic acid, (c) hypophospho-... 

Write formulas for each of the following compounds (a) carbon tetrabromide, (b) sulfur dibromide, and (c) sulfur hexafluoride. 

Name and write formulas for each of the following (a) the compound of sodium and bromine (b) the compound of magnesium and bromine and (c) the compound of aluminum and bromine. 

Using the periodic table if necessary, write formulas for the following compounds (a) hydrogen bromide, (b) magnesium chloride, (c) barium sulfide, (d) aluminum fluoride, (e) beryllium bromide, (/) barium selenide, and (g) sodium iodide. 

Ans. Selenium is below sulfur in the periodic table, and arsenic is below phosphorus. We write formulas analogous to those for sulfate and phosphate (ct) Sc04" and (/>) As04... 

Before you can balance a chemical equation, you have to know the formulas for all the reactants and products. If the names are given for these substances, you have to know how to write formulas from the names (Chap. 6). If reactants only are given, you have to know how to predict the products from the reactants. This latter topic is the subject of this section. 

We learned to write formulas of ionic compounds in Chaps. 5 and 6. We balanced the charges to determine the number of each ion to use in the formula. We could not do the same thing for atoms of elements in covalent compounds, because in these compounds the atoms do not have charges. In order to overcome this difficulty, we define oxidation numbers, also called oxidation states. 

Write formulas which contain only one multiple bond and no rings for all possible isomers of butadiene. Butadiene is CH2=CHCH = CH2. 

This ligand forms stable complexes known as cryptands (and it is often abbreviated as crypt in writing formulas) with cations of the group IA metals. More recently, the ligand known as cryptand has been used instead of ethylenediamine. This ligand has the molecular structure... 

Note that 2 MgBrCl "units" are formally equivalent to MgBr2 + MgCl2. Thus, we will continue to write formulas like MgBrCl to simplify the equations, although the products may simply be mixtures of the two magnesium halides. 

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