What is the total number of elements in group 17 that are gases at room temperature and standard pressure?

Only to elements are gases at room temperature and standard pressure.

Fluorine and chlorine.

Explanation:

The group 17 is called halogen.

There are five elements in halogen group.

All halogens required one electrons to complete the octet and to get the noble gas electronic configuration.

All halogen elements have seven valance electrons.

Halogen elements:

Fluorine, chlorine, Bromine, iodine and astatine

Fluorine is gas at room temperature which s 25°C and standard pressure which is 1 atm.

It is present in the from of F₂.

Chlorine is also gas at room temperature and standard pressure.

It is present in the from of Cl₂.

The bromine is liquid under these condition.

Iodine and astatine are solids.

As we move down the group their melting and boiling points increases.

the answer is:  

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