The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table.
〔化〕原子序数（符号：Z）
Example sentencesExamples
In a neutral atom, the number of electrons is equal to the number of protons, therefore, the atomic number also indicates the number of electrons in an atom.
There, elements are arranged according to their atomic number - the number of protons in the nuclei.
When you move down the periodic table, as the atomic numbers increase, the elements become rarer.
The existence of an element with an atomic number of 21 was predicted in 1869 by Dmitri Mendeleev.
In those cases in which the number of protons changes, the new nucleus has a different atomic number, and it therefore belongs to a different element.
The higher the atomic number, the more shells and electrons an atom will have.
We now have data on the properties of 29 new nuclei with atomic numbers between 104 and 118.
Heavy metals are metallic elements that have a high atomic number and are poisonous to living organisms.
Definition of atomic number in US English:
atomic number
nounəˈtɑmɪk ˈnəmbər
Chemistry
The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.
〔化〕原子序数（符号：Z）
Example sentencesExamples
Heavy metals are metallic elements that have a high atomic number and are poisonous to living organisms.
When you move down the periodic table, as the atomic numbers increase, the elements become rarer.
In those cases in which the number of protons changes, the new nucleus has a different atomic number, and it therefore belongs to a different element.
There, elements are arranged according to their atomic number - the number of protons in the nuclei.
The existence of an element with an atomic number of 21 was predicted in 1869 by Dmitri Mendeleev.
In a neutral atom, the number of electrons is equal to the number of protons, therefore, the atomic number also indicates the number of electrons in an atom.
We now have data on the properties of 29 new nuclei with atomic numbers between 104 and 118.
The higher the atomic number, the more shells and electrons an atom will have.