Explain the first ionization energy of lithium is greater than that of sodium

Lithium is an entire energy level smaller than sodium. Because of this, the electrons are more strongly attracted to the protons in the nucleus. The more energy levels you have, the easier it is to pull valence electrons from the outer energy shell, therefore, sodium has a smaller first ionization energy than lithium.

Source(s):
General Chemistry I Class in college

I agree with the response by v. Here is another way of saying the same thing.

Li has +3 charge in nucleus and 2e in the first energy level; therefore, the outside electron "sees" +1 charge.
Na has 11+ charge in nucleus and the outside electrons "sees" 1" charge. Since the one electron is farther away in Na, it is easier to split off so it requires less energy to pull it away.

Well, you see, when it comes to the first ionization energy of lithium and sodium, it's all about that atomic attraction game. Lithium is like a clingy ex, holding onto its outermost electron tighter than a toddler holds onto its favorite toy. So, it takes quite a bit of energy to pry that electron away from lithium and ionize it. On the other hand, sodium is more like that carefree friend who is just too happy-go-lucky to hold onto its electron too tightly. It's much easier to persuade sodium to let go and form a positive ion. So, in essence, lithium is just a bit more stubborn when it comes to losing its electron, making its first ionization energy greater than sodium's.

The first ionization energy of an element refers to the amount of energy that is required to remove one electron from a neutral atom of that element. In the case of lithium (Li) and sodium (Na), the first ionization energy of lithium is greater than that of sodium.

To understand why this is the case, we need to consider the electron configurations of these elements. The electron configuration of lithium is 1s²2s¹, meaning it has two electrons in the 1s orbital and one electron in the 2s orbital. Sodium, on the other hand, has an electron configuration of 1s²2s²2p⁶3s¹, with two electrons in the 1s orbital, two electrons in the 2s orbital, and six electrons in the 2p orbital, and one electron in the 3s orbital.

The first ionization energy depends on several factors such as the nuclear charge, the distance between the nucleus and the valence electrons, and the shielding effect of inner electrons. In this case, the primary factor is the nuclear charge.

Lithium has a smaller atomic number than sodium, which means it has a smaller positive nuclear charge. Since the number of protons in the nucleus determines the nuclear charge, lithium has 3 protons in its nucleus while sodium has 11 protons.

The smaller nuclear charge in lithium exerts a stronger attractive force on the electron in the valence shell compared to sodium. As a result, it is more difficult to remove an electron from the lithium atom because the valence electron is more strongly attracted to the nucleus. This requires more energy, hence the higher first ionization energy.

To obtain the specific values for the first ionization energies of lithium and sodium, you can refer to the periodic table or various reputable reference sources. The first ionization energy is typically expressed in units of kilojoules per mole (kJ/mol) or electron volts (eV).

Lithium Has a small atomic radius than sodium hence the valence electron are strongly attracted by the positive nuclear which require alot of energy to remove the valence electron