Question

The element with atomic number 26 will be found in the group:
A.2
B.8
C.6
D.10

Answer 1

Hint: The atomic number or proton number (symbol Z) of an element is the number of protons present in the nucleus of every atom of that element.

Complete step by step answer:
The atomic number gives a unique identity to a chemical element. It is equal to the charge of the nucleus.
The atomic number of an element is used to write the electronic configuration of the element.
The atomic number 26 is of iron (Fe).
Its electronic configuration is –
$$\Rightarrow Fe(26)-1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^6$$
Group number of an element is decided by the number of valence electrons in it.
The number of valence electrons is the number of electrons in the outermost shell of the atom.
In iron, the valence shell has 8 electrons, i.e., $4s^{2}3d^6$.

Hence the correct option is B.

Additional information:
 Atoms of an element contain an equal number of protons and electrons. The number of protons in an element determines its atomic number (Z). It distinguishes one element from another. The number of neutrons in an element can vary, hence producing isotopes. Isotopes are atoms of the same element that have different numbers of neutrons. Mass number (A) is the sum of the number of protons and the number of neutrons.

Note:
Since the last electron enters the 3d orbital, we will consider the 6 electrons of the 3d orbital also while counting the valence electrons. Also, 3d is to be written after 4s because of its higher energy state than 4s.