Explanation:
1. Barium (Ba) is larger than magnesium (Mg) because barium appears below magnesium on the periodic table. Explain why barium (Ba) is larger than magnesium (Mg).
Atomic radius trend along period
As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases and ionization energy increases because it is very difficult to remove the electron from atom and more energy is required.
Atomic radii trend along group:
As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased. Barium is present below the magnesium so barium have one more energy level and has bigger size.
2. When it ionizes, sodium (Na) becomes Na+. Does sodium lose an electron or gain an electron during ionization?
Sodium is metal it is present in group one. It has one valance electron. Sodium needed to lose one valance electron to complete the octet.
When it lose the electron positive ion is formed which is called cation Na⁺. The loses electron is accepted by non metal which thus becomes negative ion called anion X⁻.
For example:
Sodium chloride is ionic compound. The electronegativity of chlorine is 3.16 and for sodium is 0.93. There is large difference is present. That's why electron from sodium is transfer to the chlorine. Sodium becomes positive and chlorine becomes negative ion.
The atomic radius of sodium will bigger than sodium ion because sodium form cation which means electron is loses and thus electronic shell also decreases and thus size becomes smaller.
That's why sodium cation will smaller than neutral sodium.
While in case of anion one more electron in added so atomic size will bigger than neutral atom.
Along group when one more electron is added atomic size increases because of addition of one more energy level while along the period electron is added in same shell. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases
