Because at atmospheric pressure the boiling point is below room temperature, just like Oxygen, Nitrogen etc
Hello ur answer will be D, hope this helps :)
The symbol : 
<h3>Further explanation
</h3>
There are two components that accompany an element, the mass number and atomic number
Atoms are composed of 3 types of basic particles (subatomic particles): <em>protons, electrons, and neutrons
</em>
The Atomic Number (Z) indicates the number of protons and electrons in an atom of an element.
Atomic number = number of protons = number of electrons ⇒ neutral number
Atomic mass is the sum of protons and neutrons
Atomic Number (Z) = Atomic mass (A) - Number of Neutrons
The element has 71 electrons and a charge of +1 , so
Number of protons = 71 + 1 = 72
Number of protons = the atomic number = 72
The element with atomic number 72 is Hafnium(Hf)
The atomic mass of Hf = 178 g/mol
Answer:
+4
Explanation:
, Oxygen always works with -2. You multiply with the number of atoms -2*3= -6
S=x+(-6)=-2
x-6=-2 -> x= -2+6 -> x= +4