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Development of the Modern Periodic Table & Classification of the Elements. Sections 6.1 and 6.2. History of the Periodic Table. In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier. History of the Periodic Table.
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Development of the Modern Periodic Table & Classification of the Elements Sections 6.1 and 6.2
History of the Periodic Table • In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier.
History of the Periodic Table • In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier. • In all, there were only 23 elements on Lavoisier'slist!!!
History of the Periodic Table • In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier. • In all, there were only 23 elements on Lavoisier's list!!! • Many more elements were identified in the 1800s due to the discovery of electricity, the invention of the spectrometer, and the industrial revolution.
History of the Periodic Table • In the late 1790s, all the known elements were compiled in a list by Antoine Lavoisier. • In all, there were only 23 elements on Lavoisier's list!!! • Many more elements were identified in the 1800s due to the discovery of electricity, the invention of the spectrometer, and the industrial revolution. • The industrial revolution led to the development of chemistry-based industries such as the manufacture of petrochemicals, soaps, dyes, and so on. • By 1870, about 70 elements were known to exist.
History of the Periodic Table • With so many elements, scientists were overwhelmed with trying to memorize all the properties of each individual element. • John Newlands, in 1864, proposed an element organization system based off of the idea of octaves. • He stated that the properties of the elements repeated every eighth element when they were arranged by increasing atomic mass, hence the name “octave”.
History of the Periodic Table • In 1869, Lothar Meyer and Dmitri Mendeleev both developed an organization scheme that demonstrated a connection between atomic mass and the properties of elements. • But who is considered the father of the periodic table??? • As we learned back in Chapter 4, Mendeleev left blank spaces in his periodic table and was able to predict the properties of elements that should occupy those blank spots. • Scandium, Gallium, Germanium
History of the Periodic Table • However, Mendeleev’s periodic table was not completely correct… • Several of the elements were found to be in the wrong order if they were arranged by increasing atomic mass.
History of the Periodic Table • However, Mendeleev’s periodic table was not completely correct… • Several of the elements were found to be in the wrong order if they were arranged by increasing atomic mass. • In 1913, Henry Mosley discovered that the nucleus of each element contains a unique number of protons. • Number of protons = Atomic Number • Therefore, once the elements were arranged in order of increasing atomic number, all of the elements were in the correct order.
History of the Periodic Table • Periodic Law – Statement that there is a periodic repetition of chemical and physical properties of elements when they are arranged in order of increasing atomic #.
The Modern Periodic Table • The modern periodic table is arranged in rows, known as ____________, and columns, known as ________________. • Elements in the same ______________ typically have similar chemical properties • Groups on the periodic table designated with an “A” are known as representative elements, since they posses a wide range of chemical and physical properties
The Modern Periodic Table • The groups designated with a “B” are known as the transition elements. • Classifying the elements: • Metals • Nonmetals • Metalloids (Semimetals)
Metals • Metals are elements that are… • Shiny • Solids at room temperature • Good conductors of heat and electricity • Malleable • Ductile • Alkali metals – • Alkaline earth metals – • Transition and Inner Transition Metals
Metals • Metals are elements that are… • Shiny • Solids at room temperature • Good conductors of heat and electricity • Malleable • Ductile • Alkali metals – group 1A elements (but not H!) • Alkaline earth metals – group 2A elements • Transition and Inner Transition Metals – The group B elements on the periodic table
Metals • Transition and Inner Transition Metals – The group B elements on the periodic table • The Transition Metals are in the main portion of the periodic table • The Inner Transition Metals are found “underneath” the rest of the table • The 1st row is the Lanthanide Series • The 2nd row is the Actinide Series
Nonmetals • Nonmetals are elements that are… • Brittle and dull when solids • Generally solids or gases at room temperature • Poor conductors of heat and electricity • Halogens – • Noble Gases –
Nonmetals • Nonmetals are elements that are… • Brittle and dull when solids • Generally solids or gases at room temperature • Poor conductors of heat and electricity • Halogens – group 7A elements • Noble Gases – group 8A elements • The noble gases are extremely un-reactive
Metalloids • Metalloids (semimetals) are elements that have properties in common with both the metals and nonmetals! • The two most important metalloids are silicon and germanium
Organizing the Elements • Take a close look at the electron configurations for the following elements… • Hydrogen 1s1 • Lithium 1s22s1 • Sodium 1s22s22p63s1 • Potassium 1s22s22p63s23p64s1
Organizing the Elements • They all have the same number of valence electrons! • Atoms in the same group have similar chemical properties because they have the same number of valence electrons!!!!!
Organizing the Elements • They all have the same number of valence electrons! • Atoms in the same group have similar chemical properties because they have the same number of valence electrons!!!!! • The principle energy level of the valence electrons determines the period that the element is in on the periodic table.