Respuesta :
Answer:
[tex]1s^2\, 2s^2[/tex].
Explanation:
Electron orbitals in an atom (e.g., [tex]1s[/tex]) are denoted with:
- A number, denoting the shell (principal energy level) of this orbital, and
- A letter, denoting the shape of this orbital ([tex]s[/tex], [tex]p[/tex], [tex]d[/tex], etc.)
There are two aspects to consider when finding the electron configuration of an atom:
- The number of electrons that each type of orbitals could hold, and
- The order in which the orbitals are filled.
The [tex]s[/tex] orbital in each shell could hold up to [tex]2 \times 1 = 2[/tex] electrons (one [tex]s\![/tex] orbital per shell, with up to two electrons.)
The [tex]p[/tex] orbitals in each shell could hold up to [tex]2 \times 3 = 6[/tex] electrons (three [tex]p\![/tex] orbitals per shell, with up to two electrons in each orbital.)
The [tex]d[/tex] orbitals in each main shell could hold up to [tex]2 \times 5 = 10[/tex] electrons (five [tex]d\![/tex] orbitals per shell, with up to two electrons in each orbital.)
Refer to the order in which the orbitals are filled (Aufbau principle.)
- The first orbital to be filled would be [tex]1s[/tex] (the [tex]s[/tex] orbital of the first shell,) accommodating up to [tex]2[/tex] electrons.
- The second orbital to be filled would be [tex]2s[/tex] (the [tex]s[/tex] orbital of the second shell,) accommodating up to [tex]2[/tex] electrons.
All four electrons of Beryllium are thus assigned to the [tex]1s[/tex] and [tex]2s[/tex] orbitals. In a ground-state Beryllium atom, orbitals [tex]2p[/tex] and beyond would contain no electrons.
Notation:
- Two electrons in the [tex]1s[/tex] orbital: [tex]1s^{2}[/tex] (the superscript denotes the number of electrons in this orbital (or group of orbitals).)
- Two electrons in the [tex]2s[/tex] orbital: [tex]2s^2[/tex].
Write the non-empty orbitals in the order by which they are filled:
[tex]1s^2\, 2s^2[/tex].