Which of the following elements occur in nature as pair?
Phosphorus
Oxygen
Sulphur
Helium
Answers
Answer:
A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate/display recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties.
The second period contains the elements lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the second (n = 2) shell, more specifically its 2s and 2p subshells. Period 2 elements obey the octet rule in that they need eight electrons to complete their valence shell, where at most eight electrons can be accommodated: two in the 2s orbital and six in the 2p subshell.
Answer:
Oxygen
Explanation:
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