Question

If Z=3, what would be the valency of the element? Also name the element.

Answer 1

HINT Valency of an element is the number of electrons a metal gains or loses in order to attain noble gas configuration. This element gives a red flame in the flame test in inorganic qualitative analysis.

Complete step by step solution:
Here we are given that Z is 3 for an element and we need to find its valency.
- Z is the atomic number of an element. Atomic number of an element is equal to the number of electrons present in the atom or number of protons present in the nucleus.
- We are given that the atomic number of the atom is 3. That means that the atom has a total of 3 electrons.
- Let’s assign an electronic configuration to this element and then we will find its valence from it.
Electronic configuration : $1{s^2}2{s^1}$
- Now, the valency of an element is the number of electrons a metal gains or loses in order to attain noble gas configuration.
- We can see that if this element will lose one electron, then its new electronic configuration will be $1{s^2}$ and this is the same as noble gas helium. This element will not gain electrons as it will need to gain 7 more electrons in order to attain noble gas configuration.

- So, as this element can lose one electron, the valency of this element is one.
- The name of the element with atomic number Z=3 is Lithium.

Note: Remember that Z shows the atomic number of the element, so do not assume this as the atomic weight of an element. Note that in most of the cases, the Hund and Aufbau’s rules are followed in arrangement of electrons in orbitals.