Prelims - Lec 4 - The Atom and Electron Configuration

Isomers

Nuclides nuclides of the same element having the same protons or atomic number (Z) but different mass numbers (A).

Metastable state

is usually referred to isomers with half-lives of 10-9 seconds or longer

Isotones

Nuclides having the same number of neutron (N) but different number of proton.

Isobars

Nuclides of different elements but have the same mass number (A).

Isotopes

Nuclides of the same element having the same protons or atomic number (Z) but different mass.

numbers (A)

Nuclide

It is an atomic species with a definite number of protons and neutrons arranged in a definite order in the nucleus.

Truman P. Kohman (1947)

The word nuclide was proposed by who and when?

Radionuclides

These are nuclides that are unstable and thus decay by emission of particles or electromagnetic radiations or by spontaneous fission.

Electron Binding Energy

It is the strength of an attachment of an electron to the nucleus of an atom.

Valence Electrons

Electrons found in the outermost shell of an atom and determines the combining capacity.

Orbitals

These are complex-shaped high probability regions of space around the nucleus occupied by electron shells. Electrons are found here 95% of the time.

Sub-shell

Mini divisions within each shell or energy level. It is designated by the letters s, p, d, f, …

Shell number n

It is the principal quantum number.

Electron Configuration

The exact location of an electron orbiting the nucleus is impossible to determine at a given point in time. It is the standard notation used to describe the arrangement of electrons in orbitals around the nucleus.

Electron Shell

Atom’s outer region surrounding the nucleus. Designated by a letter (K,L,M,…) or number (1,2,3,…)

lower energy

Closer to the nucleus =

higher max no. of e-

Farther from the nucleus =