Ch 2 Periodic Table PDF

Periodic Table and Library of Chemical Elements Periodicity  Find Chemical Element Here CUTE NEVER FUN GENIUS ICONIC  What we can make from them? Barium (Ba) & Sodium (Na) Potassium (K), Fluorine (F), Carbon (C)...

Periodic Table and Library of Chemical Elements Periodicity  Find Chemical Element Here CUTE NEVER FUN GENIUS ICONIC  What we can make from them? Barium (Ba) & Sodium (Na) Potassium (K), Fluorine (F), Carbon (C) Oxygen (O) & Magnesium (Mg) 3 What is Similarity here? 4  Mendeleev’s Periodic Table In 1869, Mendeleev (Russian Scientist) classified the elements according to: increasing atomic mass similarity in chemical properties According to Mendeleev’s Periodic law: “Properties of elements are periodic functions of their Atomic Mass”. 5  Achievements of Mendeleev’s Table Prediction of properties of new elements: While arranging the elements according to their properties he left some gaps to represent the unknown elements. He even predicted the properties of unknown elements. Discovery of noble gases: noble were not discovered when Mendeleev gave his periodic table but when these gases were discovered much later, they could be placed in a separate group without disturbing the existing order. Can you justify the success of Mendeleev table? 6  Modern Periodic Law The Periodic Law states that ‘the physical and chemical properties of the elements repeat in a systematic and predictable way when the elements are arranged in order of increasing atomic number (Z)’. This was proposed by Moseley. This means that if the elements are arranged in order of their increasing atomic number, then elements with similar properties are repeated after a regular interval. Differentiate old and new periodic law. 7  Modern Periodic Table The standard form of the table consists of a grid of elements in 18 columns (Group/Family) and 7 rows (Period), with a double row of elements below that. 8  Alkali Metals The Alkali Metals are the series of elements in Group1 of the periodic table. The series consists of the elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). All of these elements have one valence electron which is easily lost to form an ion with a single positive charge. Li Atom 9  Alkaline Earth The Alkaline Earth metals are the series of elements in Group 2 of the periodic table. The series consists of the elements beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). All of these elements have two valence electrons and tend to lose both to form ions with a two plus charge. 10  Halogens The Halogens are the elements in Group 17 of the periodic table. They are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At). These elements all have seven valence electrons. They require one more electron to fill their outer electron shells, and so have a tendency to gain one electron to form a singly-charged negative ions. These negative ions are referred to as halide ions, and salts containing these ions are known as halides. 11  Noble gases The noble gases are the chemical elements in Group18 of the periodic table. They are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). They are sometimes called inert gases or rare gases. The noble gasses are all non-metals and are characterized by having completely filled shells of electrons. In general this makes them very unreactive chemically since it is difficult to add or remove electrons. 12  Properties Trends in the Table In periodic Atomic radii (Size) / Ionic Radii table there is Ionization Potential / Ionization certain periodic Energy trend in Electron Affinity properties of Electronegativity elements such Melting Point as: Metallic / Non-Metallic Character 13  Atomic Radii (Size) / Ionic Radii One way that chemists define atomic size is by using the atomic radius. The atomic radius is one-half the distance between the centers of a homonuclear diatomic molecule, as illustrated here. A diatomic molecule is a molecule made of exactly two atoms, while homonuclear means both atoms are the same element. 14  Atomic Size From top to bottom the atomic radii of the elements increase. Because number of shells increases when we move from top to bottom. So valence electrons are found farther from the nucleus. Ex Li has 2 shells but Na has 3 shells. 15  Atomic Size Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. And extra protons are being added to the nucleus. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. And valence electrons comes closer to the nucleus. 16  Atomic Size 5 electrons & 5 protons in Boron 7 electrons & 7 protons in Nitrogen This idea can be explained by using Columbic law of attraction. Fα q1q2/r2 Here q1 and q2 are positive & negative charges and r is the distance between nucleus and valence electron. When q1 or q2 value is more then F value will be more and r value will decrease. 17  Ionic Size Neutral atoms that have lost an electron becomes positively charged and are called cations. Size of a cation is smaller than the atom itself. For example the size of Na+ is smaller than that of Na. Na = 2,8,1 but Na+ = 2,8 After losing one electron outer shell will finish & size will reduce. 18  Give reason for Mg>Mg++ In some cases, whole shell may not be vanishing but size will reduce after it become cation. Because in cations, number of protons exceeds electrons. So the effect of nucleus (Zeff increases) on outer electrons increases and size will reduce. Fit in size order Mg, Mg+ and Mg++ Students need to discover one example. 19  Ionic Size Neutral atoms that have gained an electron are called anions, and they are larger than neutral atoms. For example Cl- is bigger than Cl Additional electron occupies the outer orbital. There is increased electron-electron repulsion which pushes the electrons further apart. Explain this concept by Zeff. In an anion, the number of protons is less than that of 20  Ionization Energy/Potential Ionization Energy is the energy needed to remove the most loosely attached electron, the valence electron, from an atom to form cation. The ionization energy of the elements within a period generally increases from left to right. Because size of atom is reducing. Valence electron is closer to the nucleus & difficult to remove. Within a group IP, generally decreases from top to bottom. This is due to electron shielding and bigger size. When valence electron is far from nucleus, it is remove it from the atom. 21  Electron shielding Shirt on our body protect us from heat/cold. It works as a shield between weather & our body. Same way, Electron shielding describes the ability of an atom's inner electrons to shield its positively- charged nucleus from its valence electrons. 22 Ionization Energy/Potential In 4th period in table, determine the element having minimum and maximum ionization potential. Give reason for higher IP for nitrogen, than carbon or oxygen. 23  Electron Affinity The Electron Affinity of an element: is the energy given off when a neutral atom in the gas phase gains an extra electron to form a negatively charged ion. The more negative the electron affinity value, the higher an atom's affinity for electrons. A fluorine atom in the gas phase, for example, gives off energy when it gains an electron to form a fluoride ion. F(g) + e- → F-(g) ; ∆Ho = -328.0 kJ/mol Negative charge indicates that energy is released (Given off) 24  Electron Affinity The electron affinity generally decreases (becomes less negative) going down a group because of the increase in size of the atoms. As we go down a group, the number of electrons increases. The force of repulsion between the electron being added and the electrons already present becomes larger. So adding extra electron is not energetically favored. Also newly added electron will not be close to the nucleus. 25  Electron Affinity Moving from left to right across a period, willingness of elements to accept electrons is higher due to valence shell stability (Octet Rule). It means EA is increasing in the period. Size of the atom reduces in a period. So newly added electron goes closer to the nucleus & stabilize the system. And releases energy. 26  Electronegativity Electronegativity is a measure of an atom’s tendency to attract electrons toward itself in a covalent bond. In general, electronegativity increases on passing from left to right along a period, and decreases on descending a group. Across a period, elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared with the energy required to lose electrons. 27  Electronegativity Descending a group, EN decreases because atomic number increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius, this makes Which element is more electronegative? losing electron easier. 28 Electronegativity 29  Melting Point Generally, the stronger the bond between the atoms of an element, the more energy required to break that bond. Metals generally possess a high melting point. Most non-metals possess low melting points. 30  Metallic Character The Metallic Character of an element can be defined as how readily an atom can lose an electron to form cation. From left to right across a period, metallic character decreases because is that the atoms want to obtain a full valence shell (octet rule), and adding (not losing) electrons is more favorable for nonmetals rather than metals. Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer shells are farther away. 31  Non-Metallic Character Non-Metallic character is the tendency of elements to gain electrons and form anions. An element is said to be non metallic if it gains electrons easily. Non metallic character decreases as we go down the group (why?). Non metallic character increases as we move across a period from left to right (why?). 32  Metalloids Elements which show properties of both metals and non metals, e.g. Boron, Silicon, Arsenic. 33  Self graded Quizzes https://www.cliffsnotes.com/study-guides/chemistry/che mistry/elements/quiz-discovery-and-similarity https://www.cliffsnotes.com/study-guides/chemistry/che mistry/elements/quiz-the-periodic-table https://www.cliffsnotes.com/study-guides/chemistry/che mistry/electron-configurations/quiz-the-periodic-table 34