Question

what is lithium^+2 mass number​

Answer 1

We know,

• Number of atoms in Li = 3

• Number of atoms in Li²⁺ = 3-2 = 1

Here,

• Its nucleus contains 3 neutrons.

• We know the mass number of the helium atom is 7.

• Finally, the lithium atom also contains 3 electrons since the number of electrons must equal the number of protons.

• An atom of lithium contains a nucleus surrounded by electron shells.

• Each of the sub-atomic particles has different properties, as shown in this table.

• The mass number of an atom is the total number of protons and neutrons in the nucleus.

• Lithium has 4 neutrons, so its mass number is 7.

• In a lithium 2 ion, first the single electron in the 2s orbital would be removed, followed by one of the electrons in the 1s orbital, leaving one electron in the 1s orbital.

Therefore,

Mass number of Li²⁺ = 3 + 4(He) = 7

$\huge\boxed{\bf Mass\:number\:of\:Li^{2+}=7}$