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Science has come a long way since Aristotle's theory of Air, Water, Fire, and Earth. Discover the organization and plan of the periodic table, and learn about the properties and significance of elements such as chlorine, nitrogen, silver, gold, mercury, oxygen, hydrogen, helium, sodium, iron, neodymium, and carbon. Gain insights into atomic structure, isotopes, valence electrons, and the properties of metals. This knowledge will provide a foundation for understanding the world around us.
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chlorine nitrogen silver gold mercury oxygen hydrogen helium sodium iron neodymium carbon
Elements • Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth. • Scientists have identified 90 naturally occurring elements, and created about 28 others.
Elements • The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe.
Periodic Table • The periodic table is organized by increasing atomic number. A great deal of information about an element can be gathered from its position in the period table. • For example, you can predict with reasonably good accuracy the physical and chemical properties of the element. You can also predict what other elements a particular element will react with chemically. • Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements.
Key to the Periodic Table • Elements are organized on the table according to their atomic number, usually found near the top of the square. • The atomic number refers to how many protons an atom of that element has. • For instance, hydrogen has 1 proton, so it’s atomic number is 1. • The atomic number is unique to that element. No two elements have the same atomic number.
What’s in a square? • Different periodic tables can include various bits of information, but usually: • atomic number • symbol • atomic mass • number of valence electrons • state of matter at room temperature.
Atomic Number • This refers to how many protons an atom of that element has. • No two elements, have the same number of protons. Bohr Model of Hydrogen Atom Wave Model
Atomic Mass • Atomic Mass refers to the “weight” of the atom. • It is derived at by adding the number of protons with the number of neutrons. This is a helium atom. Its atomic mass is 4 (protons plus neutrons). What is its atomic number? H
Atomic Mass and Isotopes • While most atoms have the same number of protons and neutrons, some don’t. • Some atoms have more or less neutrons than protons. These are called isotopes. • An atomic mass number with a decimal is the total of the number of protons plus the average number of neutrons.
Atomic Mass Unit (AMU) • The unit of measurement for an atom is an AMU. It stands for atomic mass unit. • One AMU is equal to the mass of one proton.
Atomic Mass Unit (AMU) • There are 6 X 1023 or 600,000,000,000,000,000,000,000 amus in one gram. • (Remember that electrons are 2000 times smaller than one amu).
Symbols • All elements have their own unique symbol. • It can consist of a single capital letter, or a capital letter and one or two lower case letters. C Carbon Cu Copper
Valence Electrons • A model of an atom may show the electrons surrounding the nucleus • Valence electrons are the electrons in the outer energy level of an atom. • These are the electrons that are lost, gained or shared when atoms bond together. • Na has 1 valence electron • Cl has 7 valence electrons
Mendeleev • 1869 -Dmitri Mendeléev created the first accepted version of the periodic table. • He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties. • Blank spaces were left open to add the new elements he predicted would occur.
Periods and Groups • Today, elements are grouped by atomic number
Elements in each family have similar properties. The first element in a period is always an extremely active solid. The last element in a period,is always an inactive gas. Metalloids are between the metals and nonmetals Groups / Families Periods • Columns of elements are called groups or families. • Each horizontal row of elements is called a period. • Elements in a period do not have similar properties. The properties vary greatly across any given row. • Columns of elements are called groups or families. • All elements in a family have the same number of valence electrons.
Properties of Metals Physical Properties Chemical Properties • reactivity – the ease and speed with which an element combines • good conductors of heat and electricity. • have luster - shininess • loses electrons in bonding • malleable - can be hammered or rolled into thin sheets • corrosion - reaction with water and air • ductility (ductile) -can be stretched into thin wires • The reactivity of metals tends to decrease as you move from left to right across the periodic table.
Alkali Metals (1) • found in the first column of the periodic table. • are shiny, soft, and silvery white. • atoms have 1 valence electron. • highly reactive; never found uncombined in nature, always in compounds • sodium compounds found in salt beds
Alkaline Earth Metals (2) • They are never found uncombined in nature. • They have two valence electrons. • Alkaline earth metals include magnesium and calcium, among others.
Transition Metals (3-11) • Transition Elements include those elements in the B families. • Many of hese arecommon metals: copper, tin, zinc, iron, nickel, gold, and silver. • They are good conductors of heat and electricity.
Transition Elements • many combine chemically with oxygen to form compounds called oxides. • colorful compounds of transition metals are often used to make paints. • less reactive • hard and shiny • good conductors of heat and electricity • Fe is used to make hemoglobin
Boron Family (13) • The Boron Family is named after the first element in the family. • Atoms in this family have 3 valence electrons. • This family includes a metalloid (boron), and the rest are metals. • This family includes the most abundant metal in the earth’s crust (aluminum).
Metals in Mixed Groups • not very reactive • lose 3-5 electrons in bonding • Al – lightweight, used in beverage cans and airplane bodies • Sn – protects Fe against corrosion, food cans • Pb – poisonous, used in auto batteries
Lanthanides Actinides
Rare Earth Elements Lanthanides • Soft, malleable, shiny, high conductivity • Made into alloys • Found together in ores in nature • Nd magnets Actinides • element 93+ are synthetic; created in a lab using a particle accelerator; unstable nuclei • U – used in nuclear reactors
Properties of Metalloids • have properties of both metals and nonmetals. • varying ability to conduct electricity depends on temperature, exposure to light, and purity • all are solids at room temperature and are brittle, hard, and somewhat reactive • Si, Ge, As are used to make semi- conductors (semiconductors are substances that conduct electricity under some conditions but not others; computer chips, transistors, and lasers Silicon
Properties of Nonmetals Chemical Physical • Most are gases. • some are very reactive while others do not form compounds • poor conductors of heat and electricity • Gain electrons when bonding with metals – Fe2O3, rust • solids are dull and brittle • share electrons when bonding with other nonmetals – H2O, water • Br is the only liquid Sulfur
Carbon Family (14) • have 4 valence electrons; C gains or shares electrons in bonding Coal • The element carbon is called the “basis of life” because all living things contain carbon. • most fuels burned for energy contain C Carbon fibers
Nitrogen Family (15) • Nitrogen and Phosphorus are nonmetals in this group • Atoms in the nitrogen family have 5 valence electrons; nonmetals gain or share 3 electrons when bonding • 78% of the atmosphere is nitrogen in the form of a diatomic molecule N2 • Nitrogen is not very reactive • Phosphorus is more reactive and is always found combined in nature. matches • Nitrogen fixation by bacteria makes nitrogen usable to plants animals
Oxygen Family (16) • Oxygen, Sulfur, and Selenium are nonmetals in this family • have 6 valence electrons; nonmetals gain or share 2 electrons when reacting sulfur • Oxygen is highly reactive and the most abundant element in the earth’s crust. It is extremely active and combines with almost all elements. • Oxygen may form diatomic (O2 used by your body) or triatomic (03 ozone)molecules • sulfur - used in production of rubber; health – drugs
Halogen Family (17) • Nonmetals in this family are fluorine, chlorine, bromine, iodine • Halogen atoms have 7 valence electrons and are very reactive. They are never found uncombined In nature • nonmetals gain or share 1 electron • React with alkali metals (1) to form salts
Noble Gases • Noble Gasesare colorless gases that are extremely un-reactive. • One important property of the noble gases is their inactivity. They are inactive because their outermost energy level is full. • Because they do not readily combine with other elements to form compounds, the noble gases are called inert. • The family of noble gases includes helium, neon, argon, krypton, xenon, and radon. • All the noble gases are found in small amounts in the earth's atmosphere.
