Various species of atoms in general.
Sub-atomic particles in the nucleus of an atom, i.e., protons and neutrons.
Atoms of an element with the same atomic number but different mass number.
Mass number (A):
Sum of the number of protons and neutrons, i.e., the total number of nucleons
Atomic number (Z):
The number of protons in the nucleus of an atom. This, when subtracted from A, gives the number of neutrons.
Atoms, having the same mass numbers but different atomic numbers, e.g., 15P32 and16S32.
Atoms having the same number of neutrons but different number of protons or mass number, e.g., 146C, 157N.
Atoms molecules or ions having the same number of electrons, e.g., N2, CO, CN-.
Atoms with the same atomic and mass numbers but different radioactive properties, e.g., uranium X (half life 1.4 min) and uranium Z (half life 6.7 hours).
Atomic mass unit:
Exactly equal to 1/12th of the mass of 6C12 atom.
(a.m.u.): 1 a.m.u. = 1.66 x10–24 g ≈ 931.5 MeV
The ion that is isoelectronic with CO is
(A) CN- (B) O2+
(C) O2- (D) N2+
Both CO and CN- have 14 electrons. Hence (A) is correct
Find the number of neutrons in a neutral atom having atomic mass 23 and number of electrons 11.
Number of protons = number of electrons = 11
Number of neutrons = atomic mass – number of protons =23–11 = 12
How many protons, electrons and neutrons are present in 0.18 g1530?
No. of neutrons in one atom = (30 – 15) = 15
0.18 g 3015P = 0.18 / 30 = 0.006 mole
Now, number of 3015P atoms in 0.006 mole = 0.006 x 6.02 x 1023
Number of electrons in 0.006 mole of 3015P = Number of protons in 0.006 mole 3015P = 15 x 0.006 x 6.02 x 1023 = 5.418 x 1022 and number of neutrons = 5.418 x 1022