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Elements An element is either classified as a metal, nonmetal or metalloid. The classification depends on the elements location on the periodic table. Metals are in pink. Nonmetals are in lime green. Metalloids are in white. B Si Ge As Sb Te Po At Elements 1 2 3 4 5 6 7 Metals are in yellow. Elements 1 2 3 4 5 6 7 Nonmetals in purple. are Elements 1 2 3 4 5 6 7 Metalloids in green. are Properties of Metals Metals are elements that have luster, conduct heat and electricity, and usually bend without breaking. Metals are also ductile (can be drawn out into a wire). Properties of Metals All metals except mercury (Hg) are solids at room temperature; in fact, most have extremely high melting points and high boiling points. Properties of Metals A metal’s reactivity is its ability to react with another substance. Metals in the first and second column of the periodic table are more reactive than other metals. Properties of Nonmetals Although the majority of the elements in the periodic table are metals, many nonmetals are abundant in nature. Properties of Nonmetals Most nonmetals don’t conduct electricity, are much poorer conductors of heat than metals, and are brittle when solid. Many are gases at room temperature; those that are solids lack the luster of metals. Properties of Nonmetals Their melting points tend to be lower than those of metals. Fluorine is the most reactive nonmetal. Properties of Metalloids Metalloids have some chemical and physical properties of metals and other properties of nonmetals. In the periodic table, the metalloids lie along the border between metals and nonmetals. Properties of Metalloids Properties of Metalloids Some metalloids such as silicon, germanium (Ge), and arsenic (As) are semiconductors. A semiconductor is an element that does not conduct electricity as well as a metal, but does conduct slightly better than a nonmetal. Objectives PSc.2.1.4 – Interpret the data presented in the Bohr model diagrams and dot diagrams for atoms and ions of elements 1 through 18. Modern View of the Atom The atom has two regions and is 3-dimensional. The nucleus is at the center and contains the protons and neutrons. Modern View of the Atom The electron cloud is the region where you might find an electron and most of the volume of an atom. Subatomic Particles Name Symbol Charge Relative mass Electron e- -1 1/2000 Proton p+ +1 1 Neutron n0 0 1 Atomic Number The atomic number of an element is the number of protons in the nucleus of an atom of that element. The number of protons determines identity of an element, as well as many of its chemical and physical properties. Mass Number The sum of the protons and neutrons in the nucleus is the mass number of that particular atom. Symbols Elements can be represented by using the symbol of the element, the mass number and the atomic number. Mass number The Atomic number X mass number is the atomic mass rounded to a whole number. Problem Determine the following for the fluorine atom depicted below. a) number of protons (9) 19 9 c) number of electrons (9) b) number of neutrons (10) d) atomic number (9) e) mass number (19) F Problem Determine the following for the bromine atom depicted below. a) number of protons (35) b) number of neutrons (45) 80 c) Br 35 number of electrons (35) d) atomic number (35) e) mass number (80) Problem If an element has an atomic number of 34 and a mass number of 78 what is the a) number of protons (34) b) number of neutrons (44) c) number of electrons (34) d) complete symbol 78 34 Se Problem If an element has 91 protons and 140 neutrons what is the a) atomic number (91) b) mass number (140) c) number of electrons (91) 231 d) complete symbol 91 Pa Cations A cation is a positive ion. It is formed when an atom loses one or more electrons. 2+ Ca Anions An anion is a negative ion. It is formed when an atom gains one or more electrons. 1Cl Problem Determine the following for the chlorine ion depicted below. a) number of neutrons (18) b) number of electrons (18) 35 1Cl 17 c) number of protons (17) d) mass number (35) e) atomic number (17) Problem Determine the following for the aluminum ion depicted below. a) mass number (27) b) number of electrons (10) 27 c) atomic number (13) d) number of protons (13) e) number of neutrons (14) 3+ Al 13 Isotopes In 1910, J.J. Thomson discovered that neon consisted of atoms of two different masses. Isotopes Atoms of an element that are chemically alike but differ in mass are called isotopes of the element. Isotopic Notation Consider the isotope of carbon that has a mass number of 14. The following are different ways to write symbols for this isotope. Carbon-14 14C C-14 14C 6 The Bohr Model of the Atom Niels Bohr, a young Danish physicist working in Rutherford’s laboratory in 1913, suggested that the single electron in a hydrogen atom moves around the nucleus in only certain allowed circular orbits. The Bohr Model of the Atom The atom looked like a miniature solar system. The nucleus is represented by the sun, and the electrons act like the planets. The Bohr Model of the Atom Nucleus Electron Orbit Energy Levels The Bohr Model of the Atom The orbits are circular and are at different levels. Amounts of energy separate one level from another. Bohr Diagrams 1) 2) 3) Find your element on the periodic table. Determine the number of electrons This is how many electrons you will draw. Bohr Diagrams Find out which period (row) your element is in. Elements in the 1st period have one energy level. Elements in the 2nd period have two energy levels, and so on. Bohr Diagrams 1) C 2) 3) Draw a nucleus with the element symbol inside. Carbon is in the 2nd period, so it has two energy levels, or shells. Draw the shells around the nucleus. Bohr Diagrams 1) C 2) 3) Add the electrons. Carbon has 6 electrons. The first shell can only hold 2 electrons. Bohr Diagrams 1) C 2) The second shell can only hold 8 electrons. The third shell can only hold 18 electrons. Bohr Diagrams 1) C 2) 3) Since you have 2 electrons already drawn, you need to add 4 more. These go in the 2nd shell. Add one at a time starting on the right side and going counter-clockwise. Bohr Diagrams Try the following elements on your own: a) H b) He c) O2d) Mg2+ e) Ne f) Ar Bohr Diagrams H Try the following elements on your own: a) H 1 electron b) He c) O2d) Mg2+ e) Ne f) Ar Bohr Diagrams He Try the following elements on your own: a) H b) He 2 electrons c) O2d) Mg2+ e) Ne f) Ar Bohr Diagrams O2- Try the following elements on your own: a) H b) He c) O2- 10 electrons d) Mg2+ e) Ne f) Ar Bohr Diagrams Mg2+ Try the following elements on your own: a) H b) He c) O2d) Mg2+ 10 electrons e) Ne f) Ar Bohr Diagrams Ne Try the following elements on your own: a) H b) He c) O2d) Mg2+ e) Ne 10 electrons f) Ar Bohr Diagrams Ar Try the following elements on your own: a) H b) He c) O2d) Mg2+ e) Ne f) Ar 18 electrons Electron Dot Diagrams ♦ An electron dot diagram illustrates valence electrons as dots (or other small symbols) around the chemical symbol of an element. Electron Dot Diagrams ♦ Each dot represents one valence electron. ♦ In the dot diagram, the element’s symbol represents the core of the atom—the nucleus plus all the inner electrons. Electron Dot Diagrams Write the symbol. ♦ Put one dot for each valence electron. ♦ Don’t pair electrons up until you have to. X Electron Dot Diagrams Electron Dot Diagrams Write a Lewis dot diagram for chlorine. Electron Dot Diagrams Write a Lewis dot diagram for calcium. Electron Dot Diagrams Write a Lewis dot diagram for potassium. CHEMICAL BONDING and CHEMICAL INTERACTIONS PSc.2.2 OBJECTIVE: Understand chemical bonding and chemical interactions. Objectives PSc.2.2.1 –Infer valence electrons, oxidation number, and reactivity of an element based on its location on the Periodic Table. Bonding and Molecules The outer electrons are involved in bonding. These are called valence electrons. Bonding and Molecules Most stable atoms have eight valence electrons. When an atom has 8 valence electrons, it is said to have an octet of electrons. The Octet Rule Oxidation Number An oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs. 1A 2A The elements in the A groups 8A 0 are called the representative 3A 4A 5A 6A 7A elements. 1A Group 1A elements have one valence electron. They form 1+ ions after losing the one valence electron. 1+ is referred to as the oxidation number for Group 1A elements. 2A Group 2A elements have two valence electrons. They form 2+ ions after losing the 2 valence electrons. 2+ is referred to as the oxidation number for Group 2A elements. Group 3A elements have three valence electrons. They form 3+ ions after losing the 3 valence electrons. 3+ is referred to as the oxidation number for Group 3A elements. 3A Group 4A elements have four valence electrons. They form 4+ ions after losing the 4 valence electrons. They could just as easily form 4- ions after gaining four additional electrons. 4A Group 4A elements could have a 4+ or 4oxidation number, depending on the element with which they are bonding. 4A Group 4A Two elements in Group 4A have multiple oxidation numbers of 2+ and 4+. These two elements are tin (Sn) and lead (Pb). Group 5A elements have five valence electrons. They form 3- ions after gaining 3 additional electrons. 3- is referred to as the oxidation number for Group 5A elements. 5A Group 6A elements have six valence electrons. They form 2- ions after gaining 2 additional electrons. 2- is referred to as the oxidation number for Group 6A elements. 6A Group 7A elements have seven valence electrons. They form 1- ions after gaining 1 additional electron. 1- is referred to as the oxidation number for Group 7A elements. 7A Group 8A elements have eight valence electrons, except helium which only has 2. Group 8A elements, with a full complement of valence electrons, are generally not reactive. 8A Question How many valence electrons are in an atom of each of the following elements? a) Magnesium (Mg) (2) b) Selenium (Se) (6) c) Tin (Sn) (4) Question Determine the oxidation number of each of the following elements. a) Potassium (K) b) Chlorine (Cl) c) Tin (IV) (Sn) (1+) (1-) (4+) Reactivity of Metals In general, the reactivity of metals increases from top to bottom and decreases from left to right. Reactivity of Metals Reactivity of Nonmetals In general, the reactivity of nonmetals increases from left to right and decreases from top to bottom.