Atomic number

  • an explanation of the superscripts and subscripts seen in atomic number notation. atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus.
    the rutherford–bohr model of the hydrogen atom (z = 1) or a hydrogen-like ion (z > 1). in this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one orbital to another be proportional to the mathematical square of atomic charge (z2). experimental measurement by henry moseley of this radiation for many elements (from z = 13 to 92) showed the results as predicted by bohr. both the concept of atomic number and the bohr model were thereby given scientific credence.

    the atomic number or proton number (symbol z) of a chemical element is the number of protons found in the nucleus of every atom of that element. the atomic number uniquely identifies a chemical element. it is identical to the charge number of the nucleus. in an uncharged atom, the atomic number is also equal to the number of electrons.

    the sum of the atomic number z and the number of neutrons n gives the mass number a of an atom. since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number a.

    atoms with the same atomic number but different neutron numbers, and hence different mass numbers, are known as isotopes. a little more than three-quarters of naturally occurring elements exist as a mixture of isotopes (see monoisotopic elements), and the average isotopic mass of an isotopic mixture for an element (called the relative atomic mass) in a defined environment on earth, determines the element's standard atomic weight. historically, it was these atomic weights of elements (in comparison to hydrogen) that were the quantities measurable by chemists in the 19th century.

    the conventional symbol z comes from the german word zahl meaning number, which, before the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table, whose order is approximately, but not completely, consistent with the order of the elements by atomic weights. only after 1915, with the suggestion and evidence that this z number was also the nuclear charge and a physical characteristic of atoms, did the word atomzahl (and its english equivalent atomic number) come into common use in this context.

  • history
  • the symbol of z
  • chemical properties
  • new elements
  • see also
  • references

An explanation of the superscripts and subscripts seen in atomic number notation. Atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus.
The Rutherford–Bohr model of the hydrogen atom (Z = 1) or a hydrogen-like ion (Z > 1). In this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one orbital to another be proportional to the mathematical square of atomic charge (Z2). Experimental measurement by Henry Moseley of this radiation for many elements (from Z = 13 to 92) showed the results as predicted by Bohr. Both the concept of atomic number and the Bohr model were thereby given scientific credence.

The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of every atom of that element. The atomic number uniquely identifies a chemical element. It is identical to the charge number of the nucleus. In an uncharged atom, the atomic number is also equal to the number of electrons.

The sum of the atomic number Z and the number of neutrons N gives the mass number A of an atom. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number A.

Atoms with the same atomic number but different neutron numbers, and hence different mass numbers, are known as isotopes. A little more than three-quarters of naturally occurring elements exist as a mixture of isotopes (see monoisotopic elements), and the average isotopic mass of an isotopic mixture for an element (called the relative atomic mass) in a defined environment on Earth, determines the element's standard atomic weight. Historically, it was these atomic weights of elements (in comparison to hydrogen) that were the quantities measurable by chemists in the 19th century.

The conventional symbol Z comes from the German word Zahl meaning number, which, before the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table, whose order is approximately, but not completely, consistent with the order of the elements by atomic weights. Only after 1915, with the suggestion and evidence that this Z number was also the nuclear charge and a physical characteristic of atoms, did the word Atomzahl (and its English equivalent atomic number) come into common use in this context.

Other Languages
Afrikaans: Atoomgetal
Alemannisch: Ordnungszahl
العربية: عدد ذري
aragonés: Numero atomico
Bân-lâm-gú: Goân-chú-hoan
беларуская: Зарадавы лік
български: Атомен номер
Boarisch: Ordnungszoi
bosanski: Atomski broj
brezhoneg: Niver atomek
Cymraeg: Rhif atomig
dansk: Atomnummer
Deutsch: Ordnungszahl
Esperanto: Atomnumero
euskara: Atomo-zenbaki
فارسی: عدد اتمی
Fiji Hindi: Atomic number
français: Numéro atomique
furlan: Numar atomic
贛語: 原子序數
한국어: 원자 번호
hrvatski: Atomski broj
Bahasa Indonesia: Nomor atom
interlingua: Numero atomic
íslenska: Sætistala
italiano: Numero atomico
Kiswahili: Namba atomia
Kreyòl ayisyen: Nonm atomik
Кыргызча: Атомдук номер
latviešu: Atomskaitlis
Lëtzebuergesch: Uerdnungszuel
lietuvių: Atomo numeris
Limburgs: Atoomnómmer
lumbaart: Nümer atomich
македонски: Атомски број
മലയാളം: അണുസംഖ്യ
Bahasa Melayu: Nombor atom
မြန်မာဘာသာ: အက်တမ် အမှတ်စဉ်
Nederlands: Atoomnummer
日本語: 原子番号
Nordfriisk: Atoomnumer
norsk: Atomnummer
norsk nynorsk: Atomnummer
oʻzbekcha/ўзбекча: Atom raqami
پنجابی: ایٹمی نمبر
Plattdüütsch: Atomtall
português: Número atómico
română: Număr atomic
Runa Simi: Iñuku ñiqi
русиньскый: Протонове чісло
Seeltersk: Atomtaal
Simple English: Atomic number
slovenčina: Protónové číslo
slovenščina: Vrstno število
Soomaaliga: Tiro atam
српски / srpski: Атомски број
srpskohrvatski / српскохрватски: Atomski broj
Sunda: Nomer atom
svenska: Atomnummer
தமிழ்: அணு எண்
Türkçe: Atom numarası
українська: Атомний номер
Tiếng Việt: Số nguyên tử
Võro: Aadomarv
文言: 原子序
West-Vlams: Atoomnummer
吴语: 原子序数
ייִדיש: אטאם נומער
粵語: 原子序數
中文: 原子序数