Answer:- 
molecules.
Solution:- The grams of tetrabromomethane are given and it asks to calculate the number of molecules.
It is a two step unit conversion problem. In the first step, grams are converted to moles on dividing the grams by molar mass.
In second step, the moles are converted to molecules on multiplying by Avogadro number.
Molar mass of 
= 12+4(79.9) = 331.6 g per mol
let's make the set up using dimensional analysis:
= molecules
So, there will be molecules in 250 grams of .
Answer:
fluorine
Explanation:
because it is at the top of the halogen group, which is the second to right group on the periodic table. With halogens, the higher an element is in the column, the more reactive it is. Halogens are reactive because the outer shells that orbit the nucleus lack electrons.
also because it has low dissociation energy and the valence bonding is seen close to the nucleus hence the attraction for a new electron is greater and can gain an extra electron more easily.-if ur in a higer grade u will understand this
(a) chlorine gains an electron from a sodium atom
Answer:
410 nm
Explanation:
The highest frequency is associated with the shortest wavelength. Of those listed, 410 nm is the shortest.
