1916-1930

First Great Migration. was the movement of six million African-Americans out of the rural Southern United States to the urban Northeast, Midwest, and West that occurred between 1916 and 1940. In the early 1900s, more than 90 percent of the African-American population lived in the American South and in 1900, only one-fifth of African-Americans living in the South were living in urban areas.

1980-1988

On 22 September 1980 Iraq invaded Iran to replace Iran as the dominant Persian Gulf state, resulting in stalemate with both sides claim victory Iraq failing to annex Iranian territories and Iran failing to topple Saddam Hussein

The periodic table was created by Dmitry Mendeleyev (1869) at University of St. Petersburg.

Scientists have discovered 94 naturally occurring. Majority (over three-fourths) of the natural elements are metals. The periodic table is the set of the elements written in a fashion pointing out the similarities in the properties of the elements.

The chemical properties of an element are dependent on the number of electrons in its outer shell. In the periodic table elements of the same group have the same number of electrons in the outer shell and have similar properties. The properties change gradually along periods (rows) in the table.  The major groups are 

1) Metals: Group 1A (alkali metals), 2A (alkaline earth metals), and 3-12. (good conductors of heat, malleable, ductile and shiny look). 

2) Non-metals: (poor conductors of heat, non-malleable or ductile and not shiny (Nitrogen, Oxygen)

3) Halogens: Group 7A/17 (reactive nonmetals) (fluorine (F), chlorine (Cl), bromine (Br), and iodine (I))

4) Noble gases: Group 8A / 18th (colorless and unreactive) (Helium, Neon, Argon)

Most reactive metal francium (man-made)

Most reactive metal is cesium (natural)

Least reactive element Helium 

Most electronegative fluorine 

Least electronegative francium

Lowest density Hydrogen 

Highest density Osmium.

Most common element Hydrogen

Most abundant element on earth’s crust oxygen (followed by silicon)

Most abundant element by weight iron

Rarest or scarcest element is astatine 

Lightest element Hydrogen 

Heaviest natural element is the metal uranium

Most flammable element hydrogen

Most flammable chemical chlorine trifluoride, ClF3.

Element with the highest melting point Calcium

Element with the lowest melting point Helium 

Element with the highest sublimation point Calcium

Most expensive natural element Lutetium

most conductive silver

least conductive Sulphur

highest measured radioactivity comes from the element polonium.

Most corrosive-resistant iridium

Copper is also the only metal that is naturally antibacterial

QUESTIONS

1. How far is the moon from the Earth?
2. How do we better know Theodor Seuss Geisel?
3. According to Egyptian mythology, a criosphinx is a figure that has the body of a lion and the head of a what?
4. Which animal has the biggest brain?
5. How long does Haley’s comet take how long to orbit the sun?

ANSWERS