Elements & Their Properties John Newlands 1837-1898 Dmitri Mendeleev.
Chapter 5- Section 1 Arranging the Elements. A Russian chemist named Dmitri Mendeleev was the first...
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Transcript of Chapter 5- Section 1 Arranging the Elements. A Russian chemist named Dmitri Mendeleev was the first...
A Russian chemist
named Dmitri Mendeleev was the first person to determine a pattern for the elements.
Mendeleev noted that there was a pattern within the properties of elements. He could then organize the elements depending on their atomic mass.
Atomic mass is the weighted average of the masses of all of the naturally occurring isotopes of an element. It is measured in atomic mass units.
To calculate the atomic mass:
• Multiply the mass# of each isotope (P+N) by its % amount in decimal form.
• Add the two numbers together = atomic mass.
• EXAMPLE:• Chlorine• Cl-35 (76% of chlorine in nature)• Cl-37 (24% of chlorine in nature)• (35x0.76)=26.6• (37x0.24)= 8.9 • 26.6+8.9=35.5amu
The properties of elements change in a periodic way, which means in a regular, repeating pattern. This is how the periodic table got its name.
The periodic law states that the chemical
and physical properties of elements are periodic
functions of their atomic number.
A zig zag line can be drawn on the periodic table to help remind you of the location of each type of element.
Metals•usually solid at room temp•Shiny•malleable (flattened)•ductile (made into wire)•good conductor of heat
Non Metals
•usually gas at room temp.•non shiny•not malleable or ductile•poor conductor•brittle (can shatter)