Science One word answer.

Atomic No: 18
Electronic configuration: (2, 8, 8)
The special thing about the outermost shell is that it is completely filled with the electrons.

The neutron is a neutral particle found in the nucleus of an atom. Its relative mass is 1u. It has no charge.

Electronic configuration of element with atomic no. 12-(2, 8, 2)
So, K-2, L-8, M-2

Deuterium, Protium and Tritium are isotopes.
Argon and Calcium are isobars.

Here, A and D are isotopes as they have the same number of protons but different number of neutrons.

Nucleus is a small positively charged part at the center of an atom. Nucleus is positively charged.

J. J. Thomson.

Atomic No. = 17
E.C. = (2, 8, 7)
Valency = 8 - no. of valence electrons
Valency = 8 - 7
Valency = 1

No. of neutrons = Mass No. - Atomic no.
= 24 - 12
= 12

Proton is present in same fixed no. in the atoms of any particular element.

Maximum of 2e^- can be accommodated in innermost shell of an atom.

Protons and neutrons actually determine the mass of atom.

Similarity: A pair of isotopes have same atomic number.
Difference: A pair of isotopes have different mass numbers.

The given pair are isotopes.

Electronic configuration of hydrogen : 1

Proton has relative mass of 1u and neutron also has relative mass of 1u.
Proton has relative charge of +1u and neutron has no relative charge.

Cobalt-60 radioisotope is used in the treatment of cancer.

Electron is negatively charged particle present in atoms of all the elements.

Maximum of 32e^- can be accommodated in N shell of an atom.

Three subatomic particles present in atom are electrons, protons and neutrons.

Isobars are the atoms of different elements having different atomic numbers but the same mass number (or same atomic mass).

Maximum of 8e^- can be accommodated in outermost shell of an atom.

Because all the isotopes of an element have identical atomic configuration containing same number of valence electrons, therefore, all the isotopes of an element show identical chemical properties.
For example: Cl^-₃₅ and Cl^-₃₇, show identical chemical properties as they have same no. of 7 valence electrons.

Absolute mass of proton 1.6 × 10^-27Kg
Absolute charge of proton 1.6 × 10^-19C

Electronic configuration of given element (2, 8, 3) K-2, L-8, M-3.

lodine-131 radioisotope is used to determine the activity of thyroid gland.

Mass No. = Atomic no. + No. of neutrons

Uranium-235 isotope is used as a fuel in the reactors of nuclear power plants for generating electricity.

The fractional atomic masses of elements are due to the existence of their isotopes having different masses.

There are 3 valence electrons present in the element with atomic no. 13.
Valence shell of this atom is M.

Proton is 1840 times heavier than electron.

E.C of Nitrogen = 2, 5 So, no. of valence electrons in Nitrogen atom = 5

Formation of anode rays tells about the presence of positively charged protons in all the atoms.

Nucleus was discovered by Rutherford in the alpha particle scattering experiment.

Atomic No. of X = 16
E.C. of X = (2, 8, 6)

Rutherford discovered nucleus of an atom.

Isotopes.

The number of electrons present in the valence shell are called valence electrons.
Valence electrons are situated in the outermost shell.

Alpha-particles were used by Rutherford in his experiment on the discovery of nucleus.
Alpha-particles have +2 units of charge.

J. J. Thomson discovered electron.

Nucleus is the central part of an atom in which protons and neutrons are held together.

Formation of cathode rays tells about the presence of negatively charged electrons in all the atoms.

H–1 proton, 1 electron and no neutron.
D–1 proton, 1 electron and 1 neutron.
T–1 proton, 1 electron and 2 neutrons.

Neutron is not present in ordinary hydrogen atom.

Maximum of 18e^- can be accommodated in M shell of an atom.

The conclusion is that all the atoms contain negatively charged particles called electrons.

Radioactive isotopes are used in the treatment of cancer.
One such isotope is Cobalt-60.

Maximum of 2e^- can be accommodated in K shell of an atom.