An ion is defined as an atom or molecule that has gained or lost one or more of its valence electrons, giving it a net positive or negative electrical charge.

From atoms are labelled A to E . Atoms Mass number Atomic number A 40 20 B 19 9 C 7 3 D 16 8 E 14 7 Which one of these atoms has electronic configuration 2 , 7 ?

As the atomic number of B is 9 . So the electronic configuration of element B is 2 , 7 . The systematic distribution of electrons in the various atomic orbitals is called its electronic configuration. In the electronic configuration, electrons are distributed in various energy levels (various shells) of an atom, such as K shell, L shell, M shell, N shell, etc.

Five atoms are labelled A to E . Atoms Mass number Atomic number A 40 20 B 19 9 C 7 3 D 16 8 E 14 7 Predict which is a metal?

A and C are metals. Metals are elements that lose electrons easily, that are lustrous (reflective), malleable (can be moulded into other shapes), and are good conductors of heat and electricity.