Answer:
Ionic size increases from top to bottom within the group.
Explanation:
- Ions are formed when neutral atoms of elements gain or lose electron(s).
- The ionic radius is the distance from the nucleus of an ion to the outermost energy level.
- The ionic size or radius increases down the group as the number of energy level increases.
- Therefore, an ion of an element lower in the group will be larger than the ion of an element higher in the group.
- For example, an ion of potassium, K+, is larger in size compared to the ion of sodium, Na+ since K+ has more energy levels than Na+.
The answer is A. A mole of Cu has the same number of atoms as a mole of He atoms
The average atomic mass of the imaginary element : 47.255 amu
<h3>Further explanation </h3>
The elements in nature have several types of isotopes
Isotopes are elements that have the same Atomic Number (Proton)
Atomic mass is the average atomic mass of all its isotopes
Mass atom X = mass isotope 1 . % + mass isotope 2.% ..
isotope E-47 47.011 amu, 87.34%
isotope E-48 48.008 amu, 6.895
isotope E-49 50.009 amu, 5.77%
The average atomic mass :

Replacement I think, hope this helps ;)
Explanation: