# Chapter 5 the periodic table calculating average atomic mass

Chapter 1 Chapter 1: The Chemical World 1.

Calculating Average Atomic Mass

To define a solution precisely, we need to state its concentration: how much solute is dissolved in a certain amount of solvent. Words such as dilute or concentrated are used to describe solutions that have a little or a lot of dissolved solute, respectively, but these are relative terms whose meanings depend on various factors.

Concentration is the measure of how much of a given substance is mixed with another substance. Solutions can be said to be dilute or concentrated. A concentrated solution is one in which there is a large amount of solute in a given amount of solvent. A dilute solution is one in which there is a small amount of solute in a given amount of solvent. A dilute solution is a concentrated solution that has been, in essence, watered down. Think of the frozen juice containers you buy in the grocery store.

What you have to do is take the frozen juice from inside these containers and usually empty it into 3 or 4 times the container size full of water to mix with the juice concentrate and make your container of juice.

Therefore, you are diluting the concentrated juice. When we talk about solute and solvent, the concentrated solution has a lot of solute versus the dilute solution that would have a smaller amount of solute. The terms "concentrated" and "dilute" provide qualitative methods of describing concentration. Although qualitative observations are necessary and have their place in every part of science, including chemistry, we have seen throughout our study of science that there is a definite need for quantitative measurements in science.

This is particularly true in solution chemistry. In this section, we will explore some quantitative methods of expressing solution concentration. There are several ways of expressing the concentration of a solution by using a percentage. Each mass must be expressed in the same units to determine the proper concentration. A saline solution with a mass of g has A dextrose also called D-glucose, C 6 H 12 O 6 solution with a mass of 2. Sometimes you may want to make up a particular mass of solution of a given percent by mass and need to calculate what mass of the solute to use.

Using mass percent as a conversion can be useful in this type of problem. The appropriate conversion factor based on the given mass percent can be used follows:. To solve for the mass of NaCl, the given mass of solution is multiplied by the conversion factor. What is the amount in g of hydrogen peroxide H 2 O 2 needed to make a 6.Many argue that modern chemical science began when scientists started exploring the quantitative as well as the qualitative aspects of chemistry.

Understanding the relationship between the masses of atoms and the chemical formulas of compounds allows us to quantitatively describe the composition of substances. An earlier chapter of this text described the development of the atomic mass unit, the concept of average atomic masses, and the use of chemical formulas to represent the elemental makeup of substances.

### 5: Molecules and Compounds

For covalent substances, the formula represents the numbers and types of atoms composing a single molecule of the substance; therefore, the formula mass may be correctly referred to as a molecular mass. The molecular formula of chloroform indicates that a single molecule contains one carbon atom, one hydrogen atom, and three chlorine atoms. The average molecular mass of a chloroform molecule is therefore equal to the sum of the average atomic masses of these atoms.

Figure 6. Likewise, the molecular mass of an aspirin molecule, C 9 H 8 O 4is the sum of the atomic masses of nine carbon atoms, eight hydrogen atoms, and four oxygen atoms, which amounts to Computing Molecular Mass for a Covalent Compound Ibuprofen, C 13 H 18 O 2is a covalent compound and the active ingredient in several popular nonprescription pain medications, such as Advil and Motrin.

What is the molecular mass amu for this compound? Solution Molecules of this compound are comprised of 13 carbon atoms, 18 hydrogen atoms, and 2 oxygen atoms. Following the approach described above, the average molecular mass for this compound is therefore:. Check Your Learning Acetaminophen, C 8 H 9 NO 2is a covalent compound and the active ingredient in several popular nonprescription pain medications, such as Tylenol. Ionic compounds are composed of discrete cations and anions combined in ratios to yield electrically neutral bulk matter.

As an example, consider sodium chloride, NaCl, the chemical name for common table salt. The formula mass for this compound is computed as Note that the average masses of neutral sodium and chlorine atoms were used in this computation, rather than the masses for sodium cations and chlorine anions.

### 13.5: Solution Concentration: Mass Percent

This approach is perfectly acceptable when computing the formula mass of an ionic compound. Even though a sodium cation has a slightly smaller mass than a sodium atom since it is missing an electronthis difference will be offset by the fact that a chloride anion is slightly more massive than a chloride atom due to the extra electron. Moreover, the mass of an electron is negligibly small with respect to the mass of a typical atom. Even when calculating the mass of an isolated ion, the missing or additional electrons can generally be ignored, since their contribution to the overall mass is negligible, reflected only in the nonsignificant digits that will be lost when the computed mass is properly rounded.

The few exceptions to this guideline are very light ions derived from elements with precisely known atomic masses. Computing Formula Mass for an Ionic Compound Aluminum sulfate, Al 2 SO 4 3is an ionic compound that is used in the manufacture of paper and in various water purification processes. What is the formula mass amu of this compound? For purposes of computing a formula mass, it is helpful to rewrite the formula in the simpler format, Al 2 S 3 O Following the approach outlined above, the formula mass for this compound is calculated as follows:.

Check Your Learning Calcium phosphate, Ca 3 PO 4 2is an ionic compound and a common anti-caking agent added to food products. What is the formula mass amu of calcium phosphate?Mechel Golenberke: My First Website.

Chapter 5 Note Guide. Links on Periodic Table 5. Active Art — Periodic Table 5. Links on Periodic Law 5. The periodic table is a chart which arranges all of the known elements according to their atomic numbers. The columns in the periodic table are called families or groups. The rows are called periods.

The elements to left of the periodic table are metals while the elements in the top right are non metals. All metals are solid at normal temperatures while non-metals are liquid or gaseous. Metalloids have properties of both metals and non-metals. Articles on Elements 5. The s-block elements share electron configurations. Group 1 are the alkali metals which have one valence electron. They have low ionization energies which makes them very reactive.

Group 2 is the alkali earth metals which have two valence electrons, filling their s sublevel. Because they have 2 valence electrons they are less reactive than group 1. Hydrogen is a nonmetal grouped with the alkali metals because it has one electron in its valence shell.

The p-block elements are found on the right side of the periodic table. They include the boron, carbon, nitrogen, oxygen and florine families in addition to the noble gases. The noble gases have full p-orbital's and are nonreactive. The d-block elements are found in the middle of the period table. The d-block elements are called transition metals and have valence electrons in d orbital's.

The f-block elements ,found in the two rows at the bottom of the periodic table, are called inner transition metals and have valence electrons in the f-orbital's. Transition Metals - Inner Transition Metals Transition metals are in the d-block and have valence electrons in the d-orbital's.

They can form multiple oxidation states and form different ions. Iron, Cobalt and Nickel are ferromagnetic. Inner transition metals are in the f-block and have valence electrons in the f-orbital's. They consist of the Lanthanides and the Actinides.

The Actinides are radioactive and mostly synthetic. The Nitrogen familythe Carbon family and the Boron family are found in the p-block of the Periodic Table. The Nitrogen family is group 13, while the Carbon family is group 14 and the Boron family is group All of the elements in the Nitrogen, Carbon and Boron families have unique characteristics and are of great chemical importance. Oxygen Family The Oxygen familysometimes also known as chalcogens, is group 16 on the periodic table and consisted of oxygen, sulfur, selenium, tellurium, polonium and ununhexium.

The elements in this group show patterns in its electron configuration, especially in the outermost shells. Halogens Halogens are nonmetal elements located on the right side of the periodic table in Group 7.During these challenging times, we guarantee we will work tirelessly to support you. We will continue to give you accurate and timely information throughout the crisis, and we will deliver on our mission — to help everyone in the world learn how to do anything — no matter what.

Thank you to our community and to all of our readers who are working to aid others in this time of crisis, and to all of those who are making personal sacrifices for the good of their communities. We will get through this together. Average atomic mass is not a direct measurement of a single atom.

Instead, it is the average mass per atom for a typical sample of a given element. If you could measure the mass of billions of individual atoms, you could calculate this value the same way you would find any average. Fortunately, there is a more practical method that relies on recorded information on the rarity of different isotopes. If you need to find the average atomic mass of an element, you will need to look up the atomic mass and the abundance of each isotope in that element.

Multiply the mass times the abundance for each isotope, then add all of the results together to get the average atomic mass. For tips from our reviewer on how to convert the mass to the number of atoms, keep reading!

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Learn why people trust wikiHow. This article was co-authored by Meredith Juncker, PhD. Her studies are focused on proteins and neurodegenerative diseases. There are 7 references cited in this article, which can be found at the bottom of the page. Using the Result. Tips and Warnings.

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Things You'll Need.As early chemists worked to purify ores and discovered more elements, they realized that various elements could be grouped together by their similar chemical behaviors. One such grouping includes lithium Lisodium Naand potassium K : These elements all are shiny, conduct heat and electricity well, and have similar chemical properties.

A second grouping includes calcium Castrontium Srand barium Bawhich also are shiny, good conductors of heat and electricity, and have chemical properties in common. However, the specific properties of these two groupings are notably different from each other. For example: Li, Na, and K are much more reactive than are Ca, Sr, and Ba; Li, Na, and K form compounds with oxygen in a ratio of two of their atoms to one oxygen atom, whereas Ca, Sr, and Ba form compounds with one of their atoms to one oxygen atom.

Fluorine Fchlorine Clbromine Brand iodine I also exhibit similar properties to each other, but these properties are drastically different from those of any of the elements above. Dimitri Mendeleev in Russia and Lothar Meyer in Germany independently recognized that there was a periodic relationship among the properties of the elements known at that time. Both published tables with the elements arranged according to increasing atomic mass.

But Mendeleev went one step further than Meyer: He used his table to predict the existence of elements that would have the properties similar to aluminum and silicon, but were yet unknown. By the twentieth century, it became apparent that the periodic relationship involved atomic numbers rather than atomic masses.

The modern statement of this relationship, the periodic lawis as follows: the properties of the elements are periodic functions of their atomic numbers. A modern periodic table arranges the elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column Figure 2. Each box represents an element and contains its atomic number, symbol, average atomic mass, and sometimes name.

The elements are arranged in seven horizontal rows, called periods or seriesand 18 vertical columns, called groups. Groups are labeled at the top of each column. In the United States, the labels traditionally were numerals with capital letters. For the table to fit on a single page, parts of two of the rows, a total of 14 columns, are usually written below the main body of the table. Many elements differ dramatically in their chemical and physical properties, but some elements are similar in their behaviors.

For example, many elements appear shiny, are malleable able to be deformed without breaking and ductile can be drawn into wiresand conduct heat and electricity well. Other elements are not shiny, malleable, or ductile, and are poor conductors of heat and electricity. We can sort the elements into large classes with common properties: metals elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow ; nonmetals elements that appear dull, poor conductors of heat and electricity—shaded green ; and metalloids elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals—shaded purple.

The elements can also be classified into the main-group elements or representative elements in the columns labeled 1, 2, and 13—18; the transition metals in the columns labeled 3—12 3 ; and inner transition metals in the two rows at the bottom of the table the top-row elements are called lanthanides and the bottom-row elements are actinides ; Figure 2.

The elements can be subdivided further by more specific properties, such as the composition of the compounds they form. For example, the elements in group 1 the first column form compounds that consist of one atom of the element and one atom of hydrogen.

These elements except hydrogen are known as alkali metalsand they all have similar chemical properties. The elements in group 2 the second column form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metalswith similar properties among members of that group.

Other groups with specific names are the pnictogens group 15chalcogens group 16halogens group 17and the noble gases group 18, also known as inert gases. The groups can also be referred to by the first element of the group: For example, the chalcogens can be called the oxygen group or oxygen family. Hydrogen is a unique, nonmetallic element with properties similar to both group 1 and group 17 elements.

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For that reason, hydrogen may be shown at the top of both groups, or by itself. Click on this link for an interactive periodic table, which you can use to explore the properties of the elements includes podcasts and videos of each element. You may also want to try this one that shows photos of all the elements. Naming Groups of Elements Atoms of each of the following elements are essential for life.All Quizzes. Chapter 5: The Periodic Table Enter an answer into the box.

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Keep scrolling down for answers and more stats An arrangement of elements in columns, based on a set of properties that repeat from row to row. Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column. The close match between Mendeleev's predictions and the actual properties of new elements showed how useful his periodic table could be.

In the modern periodic table, elements are arranged by increasing atomic number number of protons. Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups. Atomic mass is a value that depends on the distribution of an element's isotopes in nature and the masses of those isotopes.

Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.

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Elements in a group have similar properties because they have the same number of valence electrons. Differences in reactivity among the alkaline earth metals are shown by the ways they react with water. No comments yet Add comment. New and Popular de en es fr it nl pl pt. Countries by First Two Letters in 90 Seconds. Countries of the World with an Empty Map.

Countries with the Most Billionaires per Capita. A row in a periodic table of elements. A column of elements in a periodic table.

The pattern of repeating properties displayed by elements in the periodic table. One twelfth the mass of a carbon atom. Elements that are good conductors of electric current and heat. Elements that form a bridge between the elements on the left and right sides of the table. Elements that are poor conductors of heat and electric current.

Elements with properties that fall between those of metals and nonmetals. An electron that is in the highest occupied energy level of an atom. The elements in Group 1A of the periodic table, not including hydrogen.

The elements in Group 2A of the periodic table.Which of the following is the term for a substance in which all the atoms have the same number of protons.

Chapter 5 The Periodic Table. Played times. Print Share Edit Delete Report an issue. Play Live Live. Finish Editing.

This quiz is incomplete! To play this quiz, please finish editing it. Delete Quiz. Question 1. The horizontal row on the periodic table is called a. A vertical column is called The number at the bottom of each square on the periodic table is the The number at the top of each square on the periodic table is the What is the chemical symbol for Lithium?

## Chapter 5: The Periodic Table

How many elements follow the periodic law? Pure forms of these elements are stored in oil so they won't react with oxygen and water in the air. Alkaline-earth metals. Diamonds are a pure form of what element? This class of elements are sometimes called "semiconductors.

The atomic number tells you what? Elements which are shiny, conduct electricity and heat are called.

## Isotopic Mass

Which element is not a metal? The atoms along the staircase are called. Which is a halogen? Which is an alkali metal?