Practice Problems:



Please read the following. As you do:highlight important details circle key vocabulary words In the margins, write questions that come up as you readThe Hitchhiker's Guide to the Periodic TableTake a nice long look at the periodic table, Mendeleev's favorite creation. Seriously. Check out the colors, the rows, the columns, and the symbols. Have you ever wondered why the table?is?the way that it?is? What was good ol' Dmitri thinking when he put certain elements in one row and other elements in a different row? At first it might seem like a random mess of numbers and letters. There is, indeed, a method to the madness. In fact, we might say? HYPERLINK "" \t "_blank" it's elementary, my dear Watson.It's human nature to organize things. Librarians organize books. Cooks organize their kitchens. Who hasn't spent time organizing their Skittles to accurately reflect the rainbow? Chemists are no different than the rest of us. Okay, maybe they're a little different.?The periodic table is the tool chemists have concocted to organize all of the?elements, which are substances (like carbon or hydrogen) that cannot be decomposed into simpler substances. You may have noticed the periodic table looks like a big rectangular-ish grid. Each element has its own cheat-sheet of chemical information found in a specific place within the grid.Don't be worried if the periodic table you're used to doesn't look?exactly?like the one above. Each periodic table is unique. Some contain more information, some less. If the bells and whistles of a? HYPERLINK "" \t "_blank" fancy table?don't appeal to you, stick to a more basic table like the one? HYPERLINK "" \t "_blank" here.?Let's take a closer look within an individual periodic table box. Pick your favorite element…Cobalt, you say? It wouldn't have been our first choice, but if you insist. (Just kidding. We love all the elements equally.)One piece of information found in every periodic table is the?atomic number?(located in the upper left-hand corner in the example above). This value, unique to each element, indicates the number of protons present in the nucleus of an atom. For cobalt, the atomic number is 27, because all cobalt atoms have 27 protons. Clever, is it not?All periodic tables also contain the?chemical symbols?for each element. These symbols are simple two-letter abbreviations of the elements' names. For many elements, like Cobalt, the symbol is just the first two letters of the name…like Co. For other elements the symbols are not as obvious.? HYPERLINK "" \t "_blank" Mercury's chemical symbol, for example, is Hg. In case you are curious Hg is derived from the Latin word "hydrargyrum" meaning "liquid silver." Very fitting if you ask us.One final piece of information found in the elemental box of most periodic tables is the?atomic weight. As the name suggests, this is the mass of a single atom of the element. This information is very useful when solving all kinds of chemistry problems on exams and quizzes.The elements are placed in specific locations in the periodic table grid according to the way they look and act according to a concept called?periodicity. (More on that later.) Within the grid there are rows and columns that help organize elements with similar properties together. So there?was?a method to Mendeleev's madness.Horizontal rows of the periodic table are called periods.Horizontal rows of the periodic table are called?periods. Even though some boxes appear to be missing, all of the rows go left to right skipping over the blank areas. Every element in the same period has the same number of?atomic orbitals. These orbitals (s, p, d, and f) are the area around an atom where its electrons are most likely to be found.Confused? Let's take a closer look. The elements of the first row of the periodic table (colored in red, above) have a 1s orbital available for their electrons to sit in—all comfy and cozy. The elements of the second row of the periodic table, which is cleverly called the second period, have a 1s and three 1p orbitals available for their?valence electrons. These are the electrons located in the last shell or energy level of an atom. The fifth period elements have a 5s, three 5p, and five 5d orbitals available.?Vertical columns in the periodic table are called groups (or families).The vertical columns in the periodic table are called?groups?(or?families, depending on who you ask). The left-most column is called group one. The next group is called group two. Any guess what the third column is called? Hint: It starts with group and ends with three.?Each element in a particular group has the same number of valence electrons in their outer orbital. For example, lithium (Li) and sodium (Na) are both members of the group one club. Lithium has a?valence electron configuration?of 2s1, while sodium has a configuration of 3s1.This similarity is significant because valence electrons are the ones that form chemical bonds with other elements. In other words, elements of the same group tend to exhibit similar reactivity and tastes in music.The periodic table is also split into four blocks: s = red, p = green, d = yellow, and f = blue.To further complicate things and make your studies of the periodic table even more complicated, the periodic table is also broken into four?blocks. Check out the table above. Seriously, check it out. We'll wait.The first two columns (shown in red) comprise the s-block. The next 10 columns (shown in yellow) comprise the d-block. We'll let you use your super powers of deduction to determine the location of the p-block and the f-block. The highest-energy electrons of each element in a block belong to the same atomic orbital type. In other words, elements in the s-block have their highest energy electrons in an s orbital, while elements in the d-block have their highest energy electrons in a d-orbital.Main-group elements and transition elements of the periodic table.Did you ever think one table could be split into so many classifications? Well, we're not done yet. Our favorite table can also be broadly divided into?main-group elements?and?transition elements?(or?transition metals). The main-group elements are shown in red in the table above, and their properties are easily predictable based on their position in the periodic table. The transition elements are shown in yellow, and their properties are not as easily predictable.?The elements of the periodic table can also be classified into?metals, nonmetals, and?metalloids. We'll get into the nitty-gritty details of each column in the next few sections, but let's ease our way into this adventure for now.Periodic table color-blocked into metals, nonmetals, and metalloids.Metals occupy the left side of the periodic table. Check out the boxes shaded in those warm yellow and orange shades in the table above. Don't forget the two long rows at the bottom, either. Boom. Metals. They are good?conductors?of heat and electricity, which is a fancy way of saying heat or electrons can? HYPERLINK "" \t "_blank" easily flow?through the chunk of metal. Another term usually thrown around when talking about metals is?malleability, which means metals can be? HYPERLINK "" \t "_blank" pounded?into flat sheets or different shapes. Good examples of metals that we're all familiar with are iron (Fe), silver (Ag), and sodium (Na).On the right side of the periodic table, colored in that awesome purples, pinks, and blues are the elements cleverly named the nonmetals. These elements have properties that are more varied than their metallic cousins. Some are solids at room temperature like carbon (C), while others are gases like helium (He) or oxygen (O). Nonmetals tend to be poor conductors of heat and electricity.The elements in that funky zigzag line shaded in green in the periodic table above are called metalloids. These elements are neither metals nor nonmetals, but they do share some properties with both groups. For example, metalloids can conduct electricity like metals. Silicon (Si) is a super example of a metalloid element.Silicon (Si) is a metalloid.While we won't go into specific details about the f-block in this module it is important for you to know that there are two types of compounds in this series. The first row of the f-block is called the lanthanides. The second row of the f-block is called the actinides.Brain SnackThe only letter that does not appear anywhere on the periodic table is the letter JPractice Problems: The recurring pattern in the properties of the elements when they are arranged in order of increasing atomic number is called _________.A. the periodic lawB. Dimitri's lawC. Mendeleev's lawD. the elemental lawE. none of the above2. In the first periodic table, elements were arranged by increasing ______.A. sizeB. atomic numberC. molecular weightD. relative massE. none of the above3. In the modern periodic table elements are arranged from left to right by _______.A. increasing atomic numberB. decreasing atomic numberC. increasing molecular weightD. decreasing molecular weight?E. none of the above4. The gaps or blank spaces in the first periodic table allowed Mendeleev to _____.A. take a napB. trick question—there were no gapsC. predict the abundance of undiscovered elementsD. predict the properties of undiscovered elementsE. none of the above5. There are ____ known elements today.A. 42B. 63C. 100D. 108E. 118The Periodic Table is Oh So TrendyAt this point, we've examined various elemental occupants of the periodic table. Trust us, understanding general trends within families will come in handy one day, either on a test or when playing?Jeopardy!. But that's not all the periodic table has to offer. The truth is, if you look at the table as a whole, some even more powerful trends start to emerge that can help us compare elemental properties and even predict reactivity. It's like having a flat, gigantic crystal ball.Atomic RadiusBy definition, the?atomic radius?is one-half the distance between nuclei of two atoms. In other words, atomic radii are used to measure atomic size. In general, atomic size decreases as we move left to right across the periodic table. This can be a little confusing, but we have you covered—read on.?As we move left to right across a period we are also observing an?increase?in atomic charge (the number of protons is increasing). This greater nuclear attraction pulls the electrons in more closely, and the atomic radii actually decrease. Think of it like a big nuclear hug. The more protons, the more love, and the electrons are pulled in closer to the nucleus.Going?down?a group, atomic radii increase. This time, we're comparing electrons in?different?shells. Electrons in a 1s orbital are closer to the nucleus than electrons in a 2s orbital. In essence, the electrons in the outer shells don't "feel" the pull of the nucleus as strongly as those that are closer to the nucleus. Think about all the funky magnets you keep on your refrigerator. You use one of the magnets to hold up your prized study hall doodle. No problem—the magnet holds the single piece of paper with ease. But then you start adding more and more pieces of paper. (You've created some mad cool doodles this week.) Eventually, as you add more and more layers, the magnet loses its hold and falls off. This is similar to the idea of electron shielding. As we add more and more orbitals, the outer elections feel less of a pull from the nucleus and are able to get further away—hence the larger atomic radii as we go down the group.Atomic radii trends in the periodic table.ElectronegativityElectronegativity?is the property describing an atom's ability to attract an electron. Electrons are drawn to elements with high electronegativites like Taylor Swift is drawn to boyfriends. Remember, elements are just dying to have a stable noble gas configuration. The elements that only need one or two extra electrons to get to that state are the most electronegative—they want electrons and they'll do anything to get them.As we move to the right across a period of elements, electronegativity increases. Atoms can either gain electrons or lose electrons. When the valence shell of an atom is less than half full, it's easier to lose an electron. (Those elements want to downsize, so they are practically giving electrons away.) When the valence shell of an atom is more than half full, it's easier to gain an electron; those elements will try to get a full shell by adding on.As we move down a group, electronegativity decreases. As we navigate down a group the atoms get bigger and bigger with more and more electrons. This means the outermost electrons get further and further away from the positively charged nucleus. The consequence? Electronegativity decreases. Again, think of the magnet being shielded by all those doodle-pages.Electronegativity trends in the periodic table.It's really important to remember these are just?trends?not rules. There are always exceptions. For example, the noble gases have negligible electronegativity values despite being on the very right hand side of the periodic table and the transition metals have only very small differences in their electronegativity values.?Knowing what we know, what is the most electronegative element??Both arrows point to fluorine.Ionization Energyis the amount of energy needed to remove an electron from an atom. Elements on the left hand side of the periodic table like alkali and alkaline earth metals have low ionization energies because losing an electron (or two) would make them achieve the noble gas configuration. Sometimes it's just easier to downsize to a lower shell, especially when you only have to lose a couple electrons to do it. Elements on the right hand side of the table have higher ionization energies because want?more?electrons, not less. Think of the elements on the right as being like? HYPERLINK "" \t "_blank" Gollum?and the golden ring represents electrons. Their electrons are precious, and it would take a lot of energy to take them away. Thus, ionization energies increase from left to right across the table—the left side is giving, the right side is Gollum.We've already figured out that as we go down a group the atoms get larger and the outermost electrons move further away from the positively charged nucleus. Which are stronger, long-distance relationships or short-distance relationships? As any rom-com fan will know, long-distance relationships rarely stick. The answer is the same for electrons. Electrons that are further away from the nucleus are not as tightly bound as electrons that are closer; therefore as we move down a group the ionization energy gets smaller.Ionization energy trends in the periodic table.The trends for electronegativity and ionization energy are eerily similar. Remember that for your next quiz.Practice Problems1. Which of the following is not a periodic trend?A. Atomic RadiiB. ReactivityC. Ionization EnergyD. Electronegativity2. Electronegativity _____ as you proceed left to right across a period and _____ as you proceed down a group.A. stays the same, increasesB. increases, decreasesC. increases, increasesD. decreases, increasesE. decreases, decreases3. Ionization Energy _____ as you proceed left to right across a period and _____ as you proceed down a group.A. stays the same, increasesB. increases, decreasesC. increases, increasesD. decreases, increasesE. decreases, decreases5. Atomic radii _____ as you proceed left to right across a period and _____ as you proceed down a group.A. stays the same, increasesB. increases, decreasesC. increases, increasesD. decreases, increasesE. decreases, decreasesDone? Please get a laptop and go to more practice ................
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