Oxygen for complete combustion
“Star cluster” is a generic way for astronomers to refer to a group of stars that formed from the same material and are gravitationally bound for at least some period of time. There are two major types of star clusters — globular clusters and open clusters — and they are actually quite different.
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REASON:
Elements which have 4 valence electrons are generally metalloids.
The metalloids show the properties of both metals and non-metals.
We know that,
no. of protons= Atomic number
So,
Atomic no.= 32
Hence,
The element is Germanium which is a metalloid with 4 valence electrons and has 32 protons in nucleus of each atom because it has atomic no. 32
HOPE IT IS USEFUL
The alkali metals, which occupy group 1 of the periodic table. This is because the valence shells of these elements have only 1 electron, so easily form an ionic bond with a non-metal compound by donating this. A cation is formed by this donation, since there is one fewer electron orbiting the nucleus than there is in the atomic form - conversely an anion is formed when an atom gains an extra electron to become negatively charged.