The eleventh element in the periodic table is sodium. The sodium atom contains a total of eleven electrons and protons. Therefore, the atomic number of sodium is 11. Sodium is an alkali metal and its symbol is ‘Na’.
What is the atomic number?
Scientist Henry Gwyn Jeffreys Moseley researched the X-ray spectrum of various elements in 1913-1914. The results of the experiment show that each element has a unique integer equal to the number of positive charges in the nucleus of that element. He named that number the order of the atoms.
Thus, the number of positive charges present in the nucleus of an element is called the atomic number of that element. The atomic number of the element is expressed by ‘Z’.
This number is equal to the serial number of the periodic table. We know that protons are located in the nucleus of an atom as a positive charge. That is the total number of protons in the atomic number.
The atom is overall charge neutral. Therefore, the number of negatively charged electrons orbiting in its orbit is equal to the number of positively charged protons in the nucleus.
Atomic number (Z) = Number of charges in the nucleus (p)
Importance of the atomic number of sodium
An atomic number is a number that carries the properties of an element. The atomic number can be used to determine the number of electrons in an element and the exact position of an element in a periodic table. The properties of an element can be determined by electron configuration.
Also, the valency and valence electrons, ionic properties of the elements are determined by the electron configuration. To determine the properties of an element, it is necessary to arrange the electrons of that element. And to arrange the electrons, you must know the number of electrons in that element.
To know the number of electrons, you need to know the atomic number of that element. We know that an equal number of protons of atomic number are located in the nucleus of the element and electrons equal to protons are in orbit outside the nucleus.
Atomic number (Z) = Number of electrons
The atomic number of sodium is 11. That is, the atom of the sodium element has a total of eleven electrons. Now the electron configuration of sodium shows that the last orbital of sodium has one electron. That is, it is possible to determine the properties of sodium from the electron configuration.
The last shell of sodium has an unpaired electron, so the valency of sodium is 1. And the last shell has a total of an electron. So, the valence electrons of sodium are one. The last electron of sodium enters the s-orbital. Therefore, sodium is the s-block element.
The electron in the last shell of sodium easily forms a bond by donating to another element. To know these properties of sodium one must know the atomic number of sodium.
Relationship between the atomic mass and sodium atomic number
We already know that the nucleus is at the center of the atom. There are two types of particles in the nucleus. One is a positively charged particle proton and the other is a charge-neutral particle neutron.
Almost all the mass of the atom is accumulated in the nucleus. Therefore, the mass of the nucleus is called atomic mass. The nucleus is made up of protons and neutrons. Therefore, atomic mass refers to the total mass of protons and neutrons.
Atomic mass (A) = nucleus mass = total mass of protons and neutrons (p + n)
Again, the mass of each proton and neutron is about 1amu. Therefore, the total number of protons and neutrons is called the atomic mass number. That is, the number of atomic masses (A) = p + n
Thus, the number of neutrons in an element is obtained from the difference between the number of atomic masses and the number of atoms. That is, neutron number (n) = atomic mass number (A) – atomic number (Z)
We know that the atomic number (Z) of sodium is 11 and the atomic mass number (A) is about 23. Neutron (n) = 23 – 11 = 12. Therefore, the number of neutrons in sodium(Na) is 12.
Based on the atomic number of the element, the mass number, and the number of neutrons, three things can be considered. Namely, isotopes, isobars, and isotones.
Properties of sodium atoms
|State at 20°C
|Electrons per shell
|2, 8, 1
|370.944 K (97.794 °C, 208.029 °F)
|1156.090 K (882.940 °C, 1621.292 °F)
|Van der Waals radius
|Pauling scale: 0.93