MENDELEEV’S PERIODIC TABLE By the middle of the 19 th century, dozens of elements had been discovered.

MENDELEEV’S PERIODIC TABLE By the middle of the 19 th century, dozens of elements had been discovered. Scientists needed a way to organize the elements in groups according to their properties.

MENDELEEV’S PERIODIC TABLE By the middle of the 19 th century, dozens of elements had been discovered. Scientists needed a way to organize the elements in groups according to their properties. Dmitri Mendeleev, a Russian chemist, arranged known elements in rows and columns according to mass and chemical properties.

MENDELEEV’S PERIODIC TABLE By the middle of the 19 th century, dozens of elements had been discovered. Scientists needed a way to organize the elements in groups according to their properties. Dmitri Mendeleev, a Russian chemist, arranged known elements in rows and columns according to mass and chemical properties. He left spaces between certain elements to account for the possibility that other undiscovered elements existed.

MENDELEEV’S PERIODIC TABLE By the middle of the 19 th century, dozens of elements had been discovered. Scientists needed a way to organize the elements in groups according to their properties. Dmitri Mendeleev, a Russian chemist, arranged known elements in rows and columns according to mass and chemical properties. He left spaces between certain elements to account for the possibility that other undiscovered elements existed. Although Mendeleev did not know about atomic structure, his table is the basis of the modern periodic table.

MODERN PERIODIC TABLE The discovery of protons and that all atoms of an element have the same number of protons led to the formation of the modern periodic table in which elements are arranged by atomic number (number of protons).

MODERN PERIODIC TABLE The discovery of protons and that all atoms of an element have the same number of protons led to the formation of the modern periodic table in which elements are arranged by atomic number (number of protons). Each row (going across) in the table is called a period. Period numbers match the number of energy levels. All of the elements in a period share the same highest energy level.

MODERN PERIODIC TABLE The discovery of protons and that all atoms of an element have the same number of protons led to the formation of the modern periodic table in which elements are arranged by atomic number (number of protons). Each row (going across) in the table is called a period. Period numbers match the number of energy levels. All of the elements in a period share the same highest energy level. Each column (going down) in the table is called a group. All of the elements in a group have the same number of electrons in their outer shells or valence electrons, and therefore have similar properties.

CLASSES OF ELEMENTS The table puts elements into classes three different ways. 1. Elements are labeled according to whether they are solids, liquids or gases at room temperature. (Color of the letters).

CLASSES OF ELEMENTS The table puts elements into classes three different ways. 1. Elements are labeled according to whether they are solids, liquids or gases at room temperature (Color of the letters). 2. Elements are divided into those that are found in nature and those that are man made (Man made are white letters).

CLASSES OF ELEMENTS The table puts elements into classes three different ways. 1. Elements are labeled according to whether they are solids, liquids, or gases at room temperature. (Color of the letters). 2. Elements are divided into those that are found in nature and those that are man made. (Man made are white letters). 3. Elements are classified by their properties: metals, non-metals, and metalloids. (Color of the boxes).

CLASSES OF ELEMENTS Most elements are metals – good conductors of heat and electricity, solids at room temperature, malleable (not brittle).

CLASSES OF ELEMENTS Most elements are metals – good conductors of heat and electricity, solids at room temperature, malleable (not brittle). Transition metals are in columns 3 through 12 or Groups with a B and have similar properties.

CLASSES OF ELEMENTS Most elements are metals – good conductors of heat and electricity, solids at room temperature, malleable (not brittle). Transition metals are in columns 3 through 12 and have similar properties. Nonmetals are poor conductors and are mostly gases at room temperature. When solid they are brittle.

CLASSES OF ELEMENTS Most elements are metals – good conductors of heat and electricity, solids at room temperature, malleable (not brittle). Transition metals are in columns 3 through 12 and have similar properties. Nonmetals are poor conductors and are mostly gases at room temperature. When solid they are brittle. Metalloids look like metals, but do not have the properties of metals.

VALENCE ELECTRONS Valence electrons are electrons in the highest occupied energy level or outer shell/ring. The number of valence electrons an element has determines which group (or column) it is found on the periodic table.

VALENCE ELECTRONS Valence electrons are electrons in the highest occupied energy level or outer shell/ring. The number of valence electrons an element has determines which group (or column) it is found on the periodic table. Elements in a group have similar properties because they have the same number of valence electrons.

ALKALI METALS Group 1A. Each element has only one valence electron. Highly reactive, so they are not found in nature by themselves, only in compounds with other elements. Reactivity increases from the top to the bottom. Soft metals, cut easily. Examples: lithium, sodium, potassium.

ALKALINE EARTH METALS Group 2A. Each element has two valence electrons. Harder than alkali metals. Examples: Calcium, makes bones and teeth; magnesium, makes chlorophyll in plants.

BORON FAMILY Group 3A. Each element has three valence electrons. Includes metals and metalloids. Examples: Aluminum (metal) and boron (metalloid).

CARBON FAMILY Group 4A. Each element has four valence electrons. Becomes more metallic as you go down the column. Examples: Carbon (nonmetal) - the basis of life; silicon (metalloid) – what rocks are made of; tin and lead (metals).

NITROGEN FAMILY Group 5A. Each element has five valence electrons. Becomes more metallic as you go down the column. Examples: Nitrogen (nonmetal) – 78% of the air on Earth, essential element for life; Phosphorus (nonmetal) - essential element for life.

OXYGEN FAMILY Group 6A. Each element has six valence electrons. Members of group have different chemical properties. Examples: Oxygen (nonmetal) – the most abundant element in Earth’s crust, essential element for life; Sulfur (nonmetal) – can be found in large deposits on its own. Creates sulfuric acid, a component of acid rain.

HALOGENS Group 7A. Each element has seven valence electrons. Highly reactive. Members of group have similar chemical properties. Examples: Fluorine (nonmetal) – helps prevent tooth decay; Chlorine (nonmetal) – component of salt and used to kill bacteria in water; Iodine (nonmetal) – needed by the human body for thyroid gland to work properly.

NOBLE GASES Group 8A. All members of group are colorless, odorless gases and nonmetals. Helium has two valence electrons, and the other noble gases have eight valence electrons. The valence shell or outer shell of all of the noble gases (including helium) are full of electrons. There is no room in their outer shells to put in more electrons Because their outer shells are full, the noble gases are extremely nonreactive. They do not want to take on or give up any electrons. Examples: Helium – lighter than air, allows balloons to float. Neon, Argon, Krypton, Xenon – when excited, give off different colors of light used in signs. Radon – radioactive health hazard in homes.