Question

The first four ionization energies in kj/mol of a certain second- row element are 900, 1757, 14,849, and 21,007. what is the likely identity of the element?

Answer 1

Answer:

Beryl­lium (Be)

Step-by-step explanation:

The ionization energy is the minimum energy needed to take out an electron completely from the valence shell of an atom in its gaseous state.

The first, second, third and the fourth ionization energy is the energy associated with the removal of first, second, third and the fourth electron, respectively.

The given ionization energies (kJ/mol) of a chemical element belonging to row 2 or period 2 are: 900; 1757; 14,849; and 21,007

Since, the third ionization energy (14,849 kJ/mol) is extremely high than the second. So the element must belong to group 2 of the periodic table.

Therefore, the chemical element that belongs to the period 2 and row 2 of the periodic table is Beryl­lium (Be).

Answer 2

Answer: Berylium (Be)

Step-by-step explanation:

The first ionisation energy is the energy required to remove one mole of the outermost electrons from one mole of gaseous atoms.

Second, third, and fourth ionisation energies are the energies required to remove the succesive mole of electrons of the same atoms

Successive ionisation energies are larger because, once you have removed the first electron you get a positive ion. Removing an electron (which is a negative charge) from a positive ion is more difficult than removing it from the neutral atom. And removing an electron from an ion with 2⁺ or  3⁺ charges is increasingly difficult.

When you find a large jump from one inoization energy to the succesive one you can predict that you are removing an electron from a closer to the nucleus orbital.

Berylium has atomic number 4. So, the number of electrons of the neutral atom is also 4. Hence, the electron configuration of beryllium is 1s² 2s².

From the given data, the first four ionization energies in kJ/mol are 900, 1757, 14,849, and 21,007.

From that you can calculate the following changes in the ionization energies:

• From first to second: 1,757 kJ/mol - 900 kJ/mol = 857 kJ/mol

• From second to third: 14,849 kJ/mol - 1,757kJ/mol = 13,092 kJ/mol

• From third to fourth: 21,007 kJ/mol - 14,849 kJ/mol = 6,158 kJ/mol

And now you can see that there is a larger jump in the energy, a greater change, required to remove the third electron.

That is explained because the first and second electron are removed from the orbital 2s while the third electron has to be removed from the orbital 1s which is closer to the nucleus. This third electron is more strongly attracted by the nucleus and substantially  more energy is required to accomplish this work.