Elements and the Periodic Table Chapter 6 (page 166) Essential question • How does knowing the periodic table help scientist identify the physical and chemical characteristics of elements? Vocabulary Section 1 • Trace amounts • Macronutrients • Trace elements • Periodic • Atomic radius • Electronegativity • Ionization energy Are you made of star dust? The Big Bang produced hydrogen and helium and a tiny bit of lithium Are you made of star dust? Other elements were created in the cores of exploding stars • Scientist believe that all elements in the universe came from only four different elements – Hydrogen 75% – Helium 25% – Lithium (trace amounts) – Beryllium (trace amounts) • Scientist believe that these elements came from nuclear reactions in distant stars • It is believed that when smaller elements reacted, they produced larger elements like carbon and oxygen • The universal reactions that created all these elements came from stars exploding, called supernova • There are about 118 known elements and they all belong to one of three categories – Metals (conduct heat and electricity) – Nonmetals (poor conductors of heat and electricity) – Metalloids (properties of both metals and nonmetals) • The human body is made up of mainly four elements – Hydrogen 63% – Oxygen 26% – Carbon 9% – Nitrogen 1.25% 99% of atoms in a human body come from only 4 elements Trace Elements • You are what you eat and the other elements that are found in your body are based on what is eaten and needed to survive • Some of those trace elements include: – Calcium – Phosphorus – Potassium – Sulfur – Sodium – Chlorine – Magnesium – Iron – iodine Macronutrients • Elements that your body needs a lot of to maintain good health. • The macronutrients your body needs are: – Hydrogen – Sodium – Potassium – Calcium – Magnesium – Carbon – Nitrogen – Oxygen – Phosphorus – Sulfur – chlorine Essential elements macronutrients: elements needed in large quantities by your body. trace elements: elements that are needed in very small quantities to maintain optimum health. • Macronutrients helps to regulate the body’s function as well as to repair damaged parts • Protein, carbohydrates, DNA, and fats are needed for the body to live and survive and are made of hydrogen, carbon, nitrogen, oxygen, phosphorous and sulfur Assignment • Take a new sheet of paper and fold it into three sections • Write your name, the title of the chapter and the number • On the first section from the sheet of paper, please write six things that you learned from your notes so far that could appear on your test. History of the Periodic Table • Sept. 1860 Karlsruhe, Germany • Mendeleev- created a table in order of increasing atomic mass • His table had the elements with similar properties grouped together • Predicted new elements Mendeleev uses density (a physical property) of atoms, and organizes them in order of increasing atomic mass. There is a pattern! Moseley and the Periodic Law • Two questions about Mendeleev’s table. • 1. Why could you arrange most elements in order of increasing atomic mass, but a few could not? • 2. What was the reason for chemical periodicity Moseley and the Periodic Law • Discovered the total positive charge on the atom’s Atomic # • When arranged by positive charge the arrangement was much improved. THE PERIODIC LAW • The physical and chemical properties of the elements are periodic functions of their atomic numbers. The Modern Periodic Table • An arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column Noble Gases • Ramsey and Strutt - discovered Argon • Ramsey found Helium, Krypton, Xenon • This added a new group to the table. Lanthanides • The Lanthanides – were completed in the early 1900’s • They are the 14 elements found at the bottom of the table from # 58 - # 71 • These elements make up their own group because they are so similar in nature Actinides • The actinides are elements that are found on the bottom of the periodic table from # 90 to # 103 • These elements are so similar in characteristics that they make up their own group • The lanthanides and the actinides contain radioactive elements Periods and Blocks of the Periodic Table • Horizontal rows- Periods • 1st row - 1s is being filled • 2nd row - 2s and 2p are filled • 3rd row - 3s and 3p are filled • 4th row - 4s then 3d then 4p are filled • 5th row - 5s then 4d then 5p are filled • 6th row - 6s then 4f then 5d then 6p filled Assignment • On the second section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test. Groups 1 and 2 • S- block groups 1 and 2 • Group 1 – alkali metals • Group 2 – alkaline-earth metals Hydrogen and Helium • Hydrogen - unique element • The properties are not like any other element • Sometimes hydrogen acts like a metal, and sometimes like a nonmetal • Helium - inert gas • Helium is unreactive in nature The d- block • Groups 3 - 12 • Metals with typical metal properties • Often called transition elements • Usually have 1, 2, or 3 electrons in their outer shell The p - block • Groups 13 -18 • s block and p block called the main block elements. • Properties vary greatly • Nonmetals • Metalloids • Metals • Halogens- F, Cl, Br, I, At The f- block • Lanthanides • Actinides • Occur between groups 3 and 4 • Fill f sublevels • Most of them are radioactive and synthetic Atomic Radii – period and group trends • Atomic Radii is the distance from the nucleus of one atom to the nucleus of the second bonded atom • The smaller the atomic radii, the stronger the bond • As you go from left to right, the atomic radius decreases (generally) Period trend • As you go from top to bottom, the atomic radius increases (due to atomic sheltering) Group trend Atomic radius Increasing atomic number Like for density, there is a repeating pattern in atomic radii. Ionization Energy • Ionization energy deals with the ability of an atom to give up an electron (increases as you go across the period, and decreases as you go down the groups) • A + energy ------à A+ + e- • Any process that results in an ion being formed is called ionization • Metals have lower energies than non metals because they want to get rid of their electrons • The following charts deals with IE (first ionization energy) Ionization energy ionization energy: the energy required to remove an electron from an atom. low high Electron Affinity • Electron affinity is the energy that occurs when a neutral atom acquires an electron to become an ion • A + e- ------à A- + energy • Out of all the elements in the periodic table group 17 (the halogens gain electrons the easiest) • Metals have a lower number because they want to lose electrons and not gain electrons Assignment • On the third section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test. Notice group 2, group 12, and group 18 Electronegativity • Electronegativity – is the measure of the ability of an atom in a chemical compound to attract electrons • Nonmetals have a higher number because they want electrons • If you subtract the lower number from the higher number you get a value that can be used with a table to indentify the type of bond – Ionic (between 3.3 and 1.7) – Polar-covalent (between 1.7 and 0.3) – Nonpolar covalent (between 0.3 and 0) – Ionic (between 3.3 and 1.7) – Polar-covalent (between 1.7 and 0.3) – Nonpolar covalent (between 0.3 and 0) Electronegativity electronegativity: the ability of an atom to attract another atom’s electrons when bound to that other atom. low high Assignment 6-1 • Write a three dollar summary paragraph about what you learned in this section along with answering the questions below. • Turn to page 192 and answer # 1- 8 on a separate sheet of paper. • Honors Chemistry Homework: page 192 # 12 - 20 Vocabulary Section 2 • Alkali metals • Alkaline earth metals • Transition metals • Halogens • Noble gases Quantum Numbers & Atomic Orbitals • Principal- dist.-n = 1,2,3,4,5,6,7 • Orbital - shape- s , p, d, f • Magnetic- orientation 1,3,5,7 • Spin- spin- +1/2, - ½ • The elements in Group 1, alkali metals, reacts easily because they lose electrons easily. • Lithium, sodium, and potassium are the most abundant of the alkali metals and they always have a”+” charge • All alkali metals have one electron in their highest unfilled outer shell • All alkali metals combine with oxygen in a 2:1 ratio (Na2O, or Li2O) • All alkali metals combine with halogens in a 1:1 ratio (NaCl, or KCl) • Alkali metals are soft and react explosively with water but their ions are used by the body in nerve signaling, water retention, and maintaining correct blood chemistry levels Alkali metals • Group two metals, alkaline metals, form positive ions (+2) since their highest unfilled outer shell has only 2 electrons • The most common of the alkaline metals are beryllium, magnesium, and calcium • The alkaline metals combine with oxygen in a 1:1 (NaO, or KO) ratio and combine with the halogens in a 1:2 ratio NaCl2 or KCl2) • Magnesium and calcium are crutial to life • Mg and Ca are needed for enzyme functions • Calcium is important for teeth, bones and also helps maintain electrical impulses and magnesium assist enzymes in the body Alkaline earth metals Transition Metals • The transition metals are at the center of the periodic table and include metals like titanium, chromium, nickel, and copper • All transition metals are solids at room temperature except mercury • They are excellent conductors of electricity • Platinum is the most dense of all of the metals with a density of 21.45 g/cm3 • The transition metals start on the fourth row of the periodic table because they all have electrons in partly filled d orbitals • There are no d orbitals in the first, second, and third rows of the periodic table Transition metals • Group 13 to 16 contains some extremely important elements such as: – carbon which is the backbone of the chemistry of life – Nitrogen which is 78% of the earth’s atmosphere (N2) – Oxygen which makes up 21% of earth’s atmosphere (O2) – Both oxygen and nitrogen accept electrons and carbon can go both ways – All elements from group 13 to 16 have partially filled p orbitals which makes them very reactive – Oxygen has two spaces in the outer p orbital and so it works hard (is reactive) in order to get the last two – Nitrogen has three spaces in the outer p orbital and so it works hard (is reactive) to get those last three Carbon, nitrogen, oxygen The electron structures makes these elements very flexible in their chemistry. Carbon can accept or Nitrogen and oxygen tend to donate electrons accept electrons Assignment • On the first section of the back side of paper, please write six things that you learned from your notes so far that could appear on your test. Halogens • Group 17 is known as the halogens and includes fluorine, chlorine, iodine, and bromine • Halogens tend to be colorless gases at room temperature (if not a gas at room temperature, they form one easily when slightly heated • The pure form of these gases are poisonous when inhaled, but the halogens in the ionic form is essential to life or to killing germs • Unlike metals, halogens grab an electron which makes them negative in charge • The halogens only have one free space in the p orbital and so they are extremely reactive in order to get that last electron • In pure form, the halogens are diatomic (F2, Cl2, Br2, I2) and are highly toxic to microorganisms, bacteria and other living things • Pure chlorine is a green gas that is foul smelling, but when combines with metals forms salts that can help life (NaCl) Halogens Noble Gases • Group 18 is known as the noble gases (neon, helium, argon, krypton) • They are called noble because they do not chemically bond with any other elements (with a 5 rare exceptions) • The name came from the social class where the peasants were not allowed to interact with the noble class people • When we look at the electron configuration of the noble gases it is easy to see why they do not react, they have full outer shells • All other elements in the periodic table combine chemically to become perfect like the noble gases • Two concepts can be learned form the noble gases: – Only electrons in an unfilled energy level are available to react and make bonds – Electrons in completely filled energy levels do not make bonds Noble gases Mendeleev left empty spaces for elements not yet discovered The first periodic table as suggested by Mendeleev in 1869 The modern periodic table Electron structure was discovered after the periodic table was developed… ... but orbitals also follow a pattern in the periodic table. Element # 117 missing here 2009-2010 Element #117 was discovered through a Russian-US collaboration. The discovery still needs to be confirmed. It is temporarily named ununseptium (Uus). Discoveries are made all the time! Assignment 6-2 • Write a three dollar summary paragraph about what you learned in this section along with answering the questions below. • Honors Chemistry Homework: page 192 # 21 - 29 Vocabulary Section 3 • Valence electrons • Lewis dot diagrams • Electron configuration Only the electrons in the highest unfilled energy level form chemical bonds. Does that mean we don’t need to worry about electrons in filled energy levels? Yes! valence electrons: electrons in the highest unfilled energy level, responsible for making chemical bonds. Remember that elements Oxygen and sulfur that belong to the same belong to the same group have similar chemical group in the properties! periodic table There are millions and millions of different kinds of matter (compounds) composed of the same 92 elements. These elements are organized in a periodic table. It is called “periodic” because there is a repeating pattern. Elements that belong to the same column have similar chemical properties. Here, we are going to go over these groups of elements Valence and Electron Configuration • The electrons that are in the filled shells are not available for bonding • Only the valence electrons can take part in the chemical bonding process • Electron configuration and the electron dot diagrams are ways to identify the free electrons and the ones that are not available for bonding • Metals in the same group react similarly since they have the same number of valence electrons in the outer shell • Non metals in the same group react similarly since they have the same number of valence electrons in the outer shell • Valence electrons are electrons found in the highest unfilled energy level (the ones available for chemical bonding) Sulfur and oxygen have the same number of valence electrons. They form similar chemical compounds. Quantum Numbers & Atomic Orbitals • Come from Schrodinger Equation • Indicate region occupied by orbital • 1.Distance from nucleus • 2. Orbital shape • 3. Orbital position on x,y,z axis Quantum Numbers & Atomic Orbitals • Principal quantum number • . Symbolized by n • . indicates the main energy level • . average distance from nucleus • . referred to as shells • . n= 1,2,3,4,5,6,7 Quantum Numbers & Atomic Orbitals • Orbital quantum number • . indicates shape • . called sublevels or subshells • . indicated by s, p, d, f • . s is spherical • . p is dumbbell shape. Quantum Numbers & Atomic Orbitals • Orbital cont. • . if n= 1 then only s is allowed • . if n= 2 then s and p • . if n = 3 then s and p and d • . if n = r then s, p, d, f Quantum Numbers & Atomic Orbitals • Magnetic quantum number • . orientation in space • . s -- one • . p -- three • . d -- five • . f -- seven Quantum Numbers & Atomic Orbitals • Principal- dist.-n = 1,2,3,4,5,6,7 • Orbital - shape- s , p, d, f • Magnetic- orientation 1,3,5,7 • Spin- spin- +1/2, - ½ Assignment • On the second section of the back side of paper, please write six things that you learned from your notes so far that could appear on your test. Determining valence electrons • Write down the electron configuration. 2 2 6 2 5 Cl = 1s 2s 2p 3s 3p Determining valence electrons • Write down the electron configuration. • Count how many electrons are in the highest s and p orbitals (it should be between 1 and 8). • These are the valence electrons. 2 + 5 = 7 valence electrons 2 2 6 2 5 Cl = 1s 2s 2p 3s 3p Determining valence electrons • Write down the electron configuration. • Count how many electrons are in the highest s and p orbitals (it should be between 1 and 8). • These are the valence electrons. 2 + 1 = 3 valence electrons 2 2 6 2 6 2 10 1 Ga = 1s 2s 2p 3s 3p 4s 3d 4p Lewis dot diagram for carbon 1s22s22p2 4 valence electrons Lewis dot diagram: a diagram showing one dot for each valence electron an atom has, these dots surround the element symbol of the atom. Lewis dot diagrams • A clever way to keep track of valence electrons is to draw Lewis dot diagrams. • A dot diagram shows the element symbol surrounded by one to eight dots representing the valence electrons. What is the dot structure for nitrogen? - Elements that belong to the same group in the Carbon has periodic table have the same number of valence 4 valence electrons electrons - Only valence electrons are involved in chemical bonding - The Lewis dot diagram is a way to show valence electrons for an atom Lewis dot diagram for carbon 1s22s22p2 4 valence electrons Try • Complete the electron configuration for the following elements: – Cl –O – Ag – Li – Mg – Ca Lewis dot diagram Assignment 6-3 • Write a three dollar summary paragraph about what you learned in this section along with answering the questions below. • Turn to page 192 and answer # 9- 11 on a separate sheet of paper. • Honors Chemistry Homework: page 192 # 30 - 39 Test: - Next week Tuesday or Thursday depending on your class. • Homework requirement: Learn all terms and concepts covered on this topic. • Make sure you have all assignments between page 192 and 195 completed and turned in by your test date.
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