To work this out you do 400÷20=20
To measure length scientists may use rulers, meter sticks, etc. and to measure mass they may use a balance.
Answer:
Explanation:
The Ce metal has electronic configuration as follows
[Xe] 4f¹5d¹6s²
After losing 4 electrons , it gains noble gas configuration ,. So Ce ⁺⁴ is stable.
Eu has electronic configuration as follows
[ Xe ] 4 f ⁷6s²
[ Xe ] 4 f ⁷
Its outermost orbit contains 2 electrons so Eu²⁺ is stable. Its +3 oxidation state is also stable.
Ce⁺²
<span>All molecules are made up of atoms.
N2 O2 and H2 exist in molecule form and not in atomic form.
They exist freely in nature as molecules.
According to above explanation,
</span><span>B. Some elements found in nature exist as molecules, is the correct answer.</span>
