Unit 4: The Periodic Table Section 1: Organizing the Elements
Early chemists used the properties of elements to sort them into groups, or triads. 1700: 13 elements About 13 elements in 1700, then Scientific process discovered many more
Dmitri Mendeleev got an idea from his favorite card game… 1864: 56 elements Newlands and Meyer arrange elements by atomic mass and notice similar properties. 1869: 63 elements Dmitri Mendeleev got an idea from his favorite card game…
1864: 56 elements Newlands and Meyer arrange elements by atomic mass and notice similar properties. 1869: 63 elements Dmitri Mendeleev got an idea from his favorite card game…
Dmitri Mendeleev got an idea from his favorite card game… 1864: 56 elements Newlands and Meyer arrange elements by atomic mass and notice similar properties. 1869: 63 elements Dmitri Mendeleev got an idea from his favorite card game… Mendeleev arranged the elements by increasing atomic mass and by similar properties.
Mendeleev’s table predicted the properties of undiscovered elements.
Elements later discovered: Gallium, Germanium, and Scandium Properties of Gallium Mendeleev’s predictions Actual Properties Atomic mass 68 69.7 Density 6.0 g/cm3 5.9 g/cm3 Appearance soft gray metal Melting point Low melting point 29.8°C Later scandium too
Elements later discovered: Gallium, Germanium, and Scandium Properties of Gallium Mendeleev’s predictions Actual Properties Atomic mass 68 69.7 Density 6.0 g/cm3 5.9 g/cm3 Appearance soft gray metal Melting point Low melting point 29.8°C Later scandium too
Dmitri Mendeleev got an idea from his favorite card game… 1864: 56 elements Newlands and Meyer arrange elements by atomic mass and notice similar properties. 1869: 63 elements Dmitri Mendeleev got an idea from his favorite card game… Mendeleev arranged the elements by increasing atomic mass and by similar properties. Moseley arranges elements by the newly discovered “atomic number.” 1913: atomic numbers
each period is an energy level Period: a row across the table. each period is an energy level
same group, similar prop’s Group : a column down the table. same group, similar prop’s
The modern periodic table arranges elements by increasing atomic number. Periodic Law: periodic repetition of properties properties change across a period. properties repeat from period to period.
3 classes of elements are: Metals Metalloids Nonmetals (most elements) Metallic less Metallic
Metals Nonmetals Metalloids luster (shiny) malleable (sheets) ductile (wires) good conductors (heat/electricity) most gases brittle solids poor conductors dull/shiny brittle semi-conductors
Quick Quiz! 1. Mendeleev arranged the elements in his periodic table in order of increasing _________ and by _________ properties. atomic number , similar number of protons , repeating number of electrons , similar atomic mass , repeating
Quick Quiz. 2. The modern periodic table is arranged by increasing.. mass number. density. atomic number. intelligence.
Quick Quiz. 3. Elements in the same group have… very little in common. the same atomic number. different chemical properties. similar chemical properties.
Quick Quiz. 4. Which one of the following is NOT a general property of metals? ductility malleability high luster poor conductor of heat and electricity
Quick Quiz. 5. Which list of elements contains only nonmetals? Sn , P , Cl S , Na , O Ge , Br , Ne O , I , H
Quick Quiz. 6. Identify each as metal, nonmetal, or metalloid: Copper: Boron: Sulfur: Sodium: Tin: Hydrogen: Metal Metalloid Nonmetal Metal Metal Nonmetal
will break rather than bend Quick Quiz. 7. Identify the following sample of an unknown substance as a metal, nonmetal, or metalloid: solid at room temp. will break rather than bend conducts electricity only at high temp’s Metalloid