Presentation on theme: "Periodic Table of Elements. Mendeleev In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table. He grouped elements."— Presentation transcript:
Mendeleev In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table. He grouped elements according to their atomic mass, and he found that the families had similar chemical properties. Blank spaces were left open to add the new elements he predicted would occur.
The most abundant element in the earth’s crust is oxygen.
Modern Periodic Table In 1914 Henry Moseley reorganized the table by the ATOMIC NUMBERS. PERIODIC LAW : PROPERTIES OF THE ELEMENTS ARE PERIODIC FUNCTIONS OF THEIR ATOMIC NUMBER.
Key to the Periodic Table Elements are organized according to their atomic number. The atomic number refers to how many protons an atom of that element has. The atomic number is unique to that element. No two elements have the same atomic number.
Atomic Mass and Isotopes The atomic mass is the weighted average of the masses of the naturally occurring isotopes.
Symbols All elements have their own unique symbol. First letter is capital. The rest lower case. C Carbon Cu Copper
Valence Electrons Valence electrons are the electrons in the outer energy level of an atom. These are the electrons that are transferred or shared when atoms bond together. In our table the valence electrons are the last electrons or the electron configuration Na 2-8-1
Properties of Metals Metals are good conductors of heat and electricity. Metals are shiny- metallic luster. Metals are ductile (can be stretched into thin wires). Metals are malleable (can be pounded into thin sheets). A chemical property of metal is its reaction with water which results in corrosion.
Properties of Non-Metals Non-metals are poor conductors of heat and electricity. Non-metals are not ductile or malleable. Solid non-metals are brittle and break easily. They are dull. Many non-metals are gases. Sulfur
Properties of Metalloids B, Si, Ge, As, Sb, Te Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than non- metals but not as well as metals. They are ductile and malleable. Silicon
METALLOIDS (locate them in the periodic table!) B Si Ge As Sb Te
Periodic Table Organization----- - Groups or Families Vertical columns in the periodic table are known as groups or families The elements in a group have similar electron configurations (same number of valence electrons)
Periodic Table Organization ---- Periods Horizontal Rows in the periodic table are known as Periods The Elements in a period undergo a gradual change in properties as one proceeds from left to right. SAME NUMBER OF SHELLS
Families Periods Columns of elements are called groups or families. Elements in each family have similar but not identical properties. For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals. All elements in a family have the same number of valence electrons. Each horizontal row of elements is called a period. The elements in a period are not alike in properties. the properties change greatly across a row. The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas. SAME NUMBER OF SHELLS
Hydrogen The hydrogen square sits atop Family but it is not a member of that family. Hydrogen is in a class of its own. It’s a gas at room temperature. It has one proton and one electron in its one and only energy level. Hydrogen only needs 2 electrons to fill up its valence shell.
Alkali Metals The alkali family is found in the first column of the periodic table. Atoms of the alkali metals have a single electron in their outermost level = 1 valence electron. They are shiny, have the consistency of clay, and are easily cut with a knife.
Alkali Metals They are the most reactive metals. They react violently with water. Alkali metals are never found as free elements in nature. They are always bonded with another element.
Alkaline Earth Metals They are never found uncombined in nature. They have two valence electrons.
Transition Metals Transition Elements include those elements in the B families. These are the metals you are probably most familiar: copper, tin, zinc, iron, nickel, gold, and silver. They are good conductors of heat and electricity.
Transition Metals The compounds of transition metals are usually brightly colored and are often used to color paints. Transition elements have 1 or 2 valence electrons, which they lose when they form bonds with other atoms. Some transition elements can lose electrons in their next-to-outermost level.
Transition Elements Transition elements have COLORED IONS
Halogen Family Halogens have 7 valence electrons, which explains why they are the most active non-metals. They are never found free in nature. Halogen atoms only need to gain 1 electron to fill their outermost energy level.
Noble Gases Noble Gases are colorless gases that are extremely un-reactive. 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. All the noble gases are found in small amounts in the earth's atmosphere.
Rare Earth Elements The thirty rare earth elements are composed of the lanthanide and actinide series. One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.
TRENDS IN THE PERIODIC TABLE -- Ionization Energy -- Electronegativity -- Ionic Radius -- Metallic Character -- Activity - reactivity
Periodic Properties Elements show gradual changes in certain physical properties as one moves across a period or down a group in the periodic table. These properties repeat after certain intervals. In other words they are PERIODIC Periodic properties include: -- Ionization Energy -- Electronegativity -- Electron Affinity -- Atomic Radius -- Ionic Radius
The radius increases on going down a group. Each additional energy level “shields” the electrons from being pulled in toward the nucleus. The radius decreases on going across a period. The radius increases on going down a group. Each additional energy level “shields” the electrons from being pulled in toward the nucleus. The radius decreases on going across a period. Atomic Radius
The radius decreases across a period because the nuclear charge is increasing and the last electrons are in the same shell. Each added electron feels a greater and greater positive charge. Large Small
ION FORMATION Metals lose electrons and become positive ions Non-metals gain electrons and become negative ions
IONIC RADIUS METALLIC Cations (positive ions) are smaller than their corresponding atoms because the ions have less electrons than the atom
CATIONS are SMALLER than the atoms from which they come.. Ionic Radius Li,152 pm 3e and 3p Li +, 78 pm 2e and 3 p + Forming a cation.
Ionic Radius for Cations (METALLIC I ONS Positive ions or cations are smaller than the corresponding atoms.
Anions (NON-METALLIC IONS) Anions (negative ions) are larger than their corresponding atoms
Ionic Radius-Anions ANIONS are LARGER than the atoms from which they come. Forming an anion. F 64 pm 9e - and 9p + F -, 133 pm 10 e - and 9 p + -
Trends in Ionization Energy Ionization energy increases across a period because the nuclear charge increases. Metals lose electrons more easily than nonmetals. Metals have low ionization energy Nonmetals lose electrons with difficulty (they like to GAIN electrons). They have high ionization energy Ionization energy is the energy required to Remove an electron from an atom
Trends in Ionization Energy The ionization energy decreases DOWN a group because going down a group the atoms have extra shells and it is easier to remove an electron from a larger atom
Electronegativity Electronegativity is a measure of the ability of an atom in a molecule to attract electrons to itself. This concept was first proposed by Linus Pauling (1901-1994). He later won the Nobel Prize for his efforts
Periodic Trends: Electronegativity In a group: Atoms with fewer energy levels can attract electrons better (less shielding). So, electronegativity increases UP in group of elements. In a period: More protons, while the energy levels are the same, means atoms can better attract electrons. So, electronegativity increases to the RIGHT in a period of elements.
METALLIC CHARACTER Metals react by losing electrons. The metallic character increases as we move down a group and to the left of the table. Francium is the most metallic element Metals have low ionization energy and low electronegativities
What does it mean to be reactive? We will be describing elements according to their reactivity. Elements that are reactive bond easily with other elements to make compounds. Some elements are only found in nature bonded with other elements. What makes an element reactive? An incomplete valence electron level. All atoms (except hydrogen) want to have 8 electrons in their very outermost energy level (This is called the rule of octet.) Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.