# How do we rationalize atomic structure in terms of atomic number and electronic structure?

##### 2 Answers
May 27, 2017
1. Nucleus
2. They have same valency

#### Explanation:

1. Protons and neutrons are the sub-atomic particles present in the centre of an atom. The electrons revolve around the nucleus in their energy levels.
2. The atoms shown in the picture have the same number of electrons in the last shell (valency shell) i.e., 7. Thus they belong to the same group. They have a valency of -1.

The atoms are flourine and chlorine, the halogens. They belong to the seventh group.

May 27, 2017

The part labelled $X$ is the nucleus..................of the atom

#### Explanation:

...........an atom is a fundamental particle that consists of a massive core, the nucleus, which itself consists of one or more massive particles. The number of such massive particles WITH A POSITIVE CHARGE gives $Z$, the atomic number, which defines the identity of the atom. Also contained in the nucleus are other massive particles called neutrons, with no net electrical charge. Short-range attractive interactions between the nuclear particles are responsible for the stability of the nucleus.

Around the nucleus, one or more electrons, particles of near zero net mass, and negative electronic charge, are conceived to whizz around at radii which dwarf nuclear dimensions. In the NEUTRAL atom, there are necessarily equal numbers of electrons, and protons, i.e. the positively charged nuclear particles.

So that's atomic physics all done in 2 paragraphs! Now onto your questions.

$\text{X=the nucleus}$

These two atoms belong in the same Group (the same column of the Periodic Table) because they have the same number of valence (i.e. outermost) electrons; 7 in each case. You should be able to tell me the name of the Group to which the atom belongs.