state the number of electrons either lost or gained in forming each ion.
Br-
As3-
1 gained
To determine the number of electrons lost or gained in forming an ion, you need to understand the concept of valence electrons.
Br- (Bromide ion):
Bromine (Br) belongs to Group 17 (Group VIIA) of the periodic table, known as the halogens. Halogens have 7 valence electrons. By gaining one electron, bromine achieves a stable electron configuration, similar to the nearest noble gas, which is krypton.
In the case of Br-, the minus sign indicates that one electron has been gained, resulting in a negative charge. Therefore, in forming the Br- ion, bromine gains one electron.
As3- (Arsenide ion):
Arsenic (As) belongs to Group 15 (Group VA) of the periodic table. Group 15 elements have 5 valence electrons. By gaining three more electrons, arsenic can achieve a stable electron configuration, similar to the nearest noble gas, which is krypton.
In the case of As3-, the number 3 next to the elemental symbol As represents the charge of the ion. Here, three additional electrons are gained, resulting in a negative charge of 3-. Therefore, in forming the As3- ion, arsenic gains three electrons.
In summary:
Br- gained 1 electron.
As3- gained 3 electrons.
To determine the number of electrons either lost or gained in forming each ion, we need to look at the electron configuration of the atom and ion.
1. Br- (Bromide ion):
Bromine (Br) has an electron configuration of 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5. To become stable, it tends to gain one electron to obtain the electron configuration of the nearest noble gas, which is argon (Ar, 1s^2 2s^2 2p^6 3s^2 3p^6). Therefore, the bromine ion (Br-) gains one electron, resulting in a net negative charge.
The number of electrons gained is:
Br- = 1 electron gained
2. As3- (Arsenide ion):
Arsenic (As) has an electron configuration of 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^3. To become stable, it tends to gain three electrons to obtain the electron configuration of the nearest noble gas, which is krypton (Kr, 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6). Therefore, the arsenide ion (As3-) gains three electrons, resulting in a net negative charge.
The number of electrons gained is:
As3- = 3 electrons gained