Answer:
1 : 2 cm/km or 
One cm represents 2 km.
Explanation:
If 3 cm represents 6 km on the earth, the ratio to consider is: 3 : 6 cm/km which is the same as:
1 : 2 cm/km or 
One cm represents 2 km.
the atomic number of a chemical element (also known as its proton number) is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus.
Hope this helped
Is there options for this??
Answer:
I guess that the atoms are:
Protons: 6 8 5 2 12 12
Neutrons: 8 8 5 3 13 14
Now, two atoms are isotopes if they share the same number of protons (so both atoms are the same element) but they have a different number of neutrons.
From the given options, the only two that have the same number of protons but a different number of neutrons are:
Protons 12, neutrons 13
and
Protons 12, neutrons 14.
These two are isiotopes.