Element Any pure substance that is made of only one kind of atom
History of Elements • Aristotle • Aristotle believed there were four “elements”: air, fire, water, and earth. • People during Aristotle’s time period knew of at least nine substances that are defined as elements today.
History of Elements • Alchemists • Alchemists tried to convert “cheap” metals, like lead, into gold. • In doing so, they developed equipment and techniques that enabled them to discover and purify substances.
History of Elements • Alchemists • Alchemy also had a philosophical, magical, and mystically religious aspect to it.
History of Elements • Alchemy was transformed into a real science after the Renaissance. • Boyle rejected Aristotle’s elements and defined an element as any substance that cannot be decomposed into simpler substances.
Element Symbols • Berzelius proposed element symbols consisting of the first two letters of the element’s Latin name.
Element Symbols • In the current periodic table, each symbol still consists of a letter or two from the element’s name. • Most of the symbols are derived from the English names instead of the Latin.
Element Symbols • You will need to memorize the symbols for several common elements.
Element Symbols • Some symbols still use letters from the element’s Latin name. • Silver, Ag - argentum • Sodium, Na - natrium • Iron, Fe - ferrum • Lead, Pb - plumbum
Element Symbols • Some elements are named for scientists, places, or colors.
Characteristics of Elements • Almost all naturally-occurring elements are solids at room temperatures. • Two are liquids, and eleven are gases.
Characteristics of Elements • Some elements naturally occur as separate atoms. • These elements are called monatomic. • They are located at the far right of the periodic table.
Characteristics of Elements • Some elements exist as molecules consisting of two atoms. • These elements are called diatomic.
Characteristics of Elements • Hydrogen, nitrogen, oxygen, and the halogens are diatomic molecules. • The halogens are the four elements on the right side of the periodic table (shaded light purple).
Characteristics of Elements The Diatomic Molecules H N O H a l o g e n s
Characteristics of Elements • Anytime an element occurs in a molecule with more than two atoms, it is called a polyatomic molecule. • Oxygen can form O3 (ozone) or O4 (tetraoxygen). • Sulfur can occur as S7, S8, or S12.
Who proposed symbols consisting of the first two letters of an element’s Latin name? Who proposed symbols consisting of the first two letters of an element’s Latin name? Who proposed symbols consisting of the first two letters of an element’s Latin name? • Aristotle • Berzelius • Boyle • The Alchemists
Which of the following is not a diatomic molecule? Which of the following is not a diatomic molecule? Which of the following is not a diatomic molecule? • Chlorine • Iodine • Oxygen • Sulfur
Organizing the Elements • In the early 1800s there was little order in the properties and symbols for the elements.
Döbereiner • Döbereiner arranged the elements with similar properties into groups of three. • These groups were calledtriads.
Döbereiner • However, a problem with this system developed. • Soon more elements were discovered, so that there were more than three similar elements in each group.
De Chancourtois • De Chancourtois graphed the atoms’ atomic mass on paper and wrapped the paper into a cylinder. • He noted that the properties repeated as the mass increased.
Newlands • Newlands arranged the elements by atomic mass. • He called his system the Law of Octaves.
phosphorus 12 magnesium 9 aluminum 10 chlorine 14 beryllium 2 nitrogen 5 silicon 11 fluorine 7 oxygen 6 sodium 8 carbon 4 sulfur 13 lithium 1 boron 3
Mendeleev • Mendeleev developed his periodic table using four techniques. 1. He arranged elements by atomic mass (as Newlands did). 2. He left blanks when properties or mass did not fit.
Mendeleev 3. He predicted properties of missing elements. 4. He placed elements with similar properties in the same column.
Mendeleev • However, there was a problem with Mendeleev’s table. • Some elements were out of order when positioned by atomic mass. • Example: Te and I
Moseley • Moseley arranged the elements according to atomic number. • This correction solved the problem with Mendeleev’s table.
Who first arranged elements by their atomic mass? • Mendeleev • Moseley • Newlands • Döbereiner
Who developed the periodic table? • Mendeleev • Moseley • Newlands • Döbereiner
Who was the first to group similar elements together? • Mendeleev • Moseley • Newlands • Döbereiner
Who changed the order of the periodic table to atomic number? • Mendeleev • Moseley • Newlands • Döbereiner
Periodic Law The chemical properties of elements vary with their atomic numbers in a periodic way.
What was wrong with Mendeleev’s periodic table? • Elements missing • No triads • Elements out of order • No pattern
The periodic law says that elements’ properties repeat based on what? • Triads • Temperature • Atomic mass • Atomic number
Modern Periodic Table • The periodic table continues to change as new elements are discovered; it is not a finished product.
Introduction There are three broad classes of elements on the periodic table. • Metals • Nonmetals • Metalloids
Metals Metals Metals
Metals • Most elements are metals. • Some metals are light, soft, and weak. • The most important characteristic of metals is that they easily lose or give up electrons.
Nonmetals Nonmetals Nonmetals
Nonmetals • The nonmetals are located on the right side of the periodic table. • The most important characteristic of nonmetals is that they gain or share electrons.
Metalloids Metalloids Metalloids