Matter and Change
Part 4: Development and Organization of the Periodic Table
TAKS Student Expectation
Integrated Physics and Chemistry (7) Science Concepts. The Student knows the relationship between properties and its components. The Student is expected to:
(D) relate the chemical behavior of an element including bonding, to its placement on the periodic table.
Elements
• element is a substance made up of similar atoms.
– All atoms of the same element have the same number of protons
• very few elements are found in their pure form in nature.
– Ex: diamond- pure carbon, oxygen in the air, and nitrogen in the air.
Introduction to the Periodic Table
The Development of the Periodic Table
• 1790 – Antonie Lavoisier (France) compiled a list of all known elements at the time – 23. • Discovery of new elements progressed rapidly during the industrial revolution.
• 1864 – John Newlands (England) noticed when elements were arranged in increasing atomic mass, similar properties occurred every eight elements, which he called octaves. • 1869- Demetri Medeleev (Russia) and Lothar Meyer (Germany) listed elements by increasing atomic mass, noticing a regular (periodic) recurrence of physical and chemical properties.
– 1. Mendeleev’s chart lists those elements with similar properties side by side. Increasing in atomic mass top to bottom. – 2. Several of the elements we know today, were still undiscovered. Using the chart Medeleev predicted the properties of Gallium 15 years before it would be discovered.
– However, with the discovery of newer elements, scientists proved that atomic mass was not the proper order.
• 1913- Henry Moselyproved that atomic number, instead of atomic mass should be used. Like Mendeleev, he also predicted several elements which were to be discovered later.
Today’s known elements
• Of the 110(or more) known elements
– around 30 are most commonly used. – around 20 are man made (synthetic elements).
• Elements can be represented by their chemical “symbol”, not abbreviation, as such, they must be written properly.
– The first letter of the symbol is always capitalized – The second letter of the symbol (if needed), is always lower-case.
– Improperly written symbols lead to mistakes
• Cu vs. CU • Co vs. CO • MgNO3 vs MnGO3.
– All known elements have been placed on the Periodic Table of the Elements.
Periods and Groups
• The periodic table organizes chemical elements according to their properties
– Periods- the horizontal rows of the periodic table – Groups- the vertical columns of the periodic chart. Elements in the same group have similar chemical and physical properties.
Group
Period