Atomic Number Examples

Posted on 30-04-2021 by admin

Learning Objective

Determine the relationship between the mass number of an atom, its atomic number, its atomic mass, and its number of subatomic particles

Key Points

Neutral atoms of each element contain an equal number of protons and electrons.
The number of protons determines an element’s atomic number and is used to distinguish one element from another.
The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess.
Together, the number of protons and the number of neutrons determine an element’s mass number.
Since an element’s isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes.

Calculate number of protons, electrons and nutron using atomic number examples and mass number example helpful for CBSE 11 Chemistry Structure of atom.

Atomic number The atomic number of an element is equal to the number of protons in the nucleus of its atom. For example, the nucleus of an oxygen atom contains eight protons and eight neutrons. Oxygen ’ s atomic number is, therefore, eight. Atomic number of an element never changes: for example, the atomic number of oxygen is always 8, and the atomic number of Chlorine is always 18. The atomic number is marked with the symbol Z, taken from a German word zahl (or atomzahl, which is 'atomic number' in German). The atomic number and the mass number of an element is usually written in the following way: The helium atom has a mass number of 4 and atomic number of 2. Example; What is the mass number and atomic number of the? Solution: Mass number = 31, atomic number = 15. Number of neutrons = mass number – atomic number.

Terms

What Is An Atomic Number

atomic massThe average mass of an atom, taking into account all its naturally occurring isotopes.
mass numberThe sum of the number of protons and the number of neutrons in an atom.
atomic numberThe number of protons in an atom.

Atomic Number

Neutral atoms of an element contain an equal number of protons and electrons. The number of protons determines an element’s atomic number (Z) and distinguishes one element from another. For example, carbon’s atomic number (Z) is 6 because it has 6 protons. The number of neutrons can vary to produce isotopes, which are atoms of the same element that have different numbers of neutrons. The number of electrons can also be different in atoms of the same element, thus producing ions (charged atoms). For instance, iron, Fe, can exist in its neutral state, or in the +2 and +3 ionic states.

Mass Number

An element’s mass number (A) is the sum of the number of protons and the number of neutrons. The small contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the mass number. Protons and neutrons both weigh about one atomic mass unit or amu. Isotopes of the same element will have the same atomic number but different mass numbers.

Scientists determine the atomic mass by calculating the mean of the mass numbers for its naturally-occurring isotopes. Often, the resulting number contains a decimal. For example, the atomic mass of chlorine (Cl) is 35.45 amu because chlorine is composed of several isotopes, some (the majority) with an atomic mass of 35 amu (17 protons and 18 neutrons) and some with an atomic mass of 37 amu (17 protons and 20 neutrons).

Given an atomic number (Z) and mass number (A), you can find the number of protons, neutrons, and electrons in a neutral atom. For example, a lithium atom (Z=3, A=7 amu) contains three protons (found from Z), three electrons (as the number of protons is equal to the number of electrons in an atom), and four neutrons (7 – 3 = 4).

Show Sources

Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:

http://www.boundless.com/
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http://en.wiktionary.org/wiki/atomic_number
Wiktionary
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http://www.boundless.com//biology/definition/atomic-mass–2
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“A-level Chemistry/OCR/Atoms, Bonds and Groups/Atoms and Reactions/Atoms.”

http://en.wikibooks.org/wiki/A-level_Chemistry/OCR/Atoms,_Bonds_and_Groups/Atoms_and_Reactions/Atoms
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http://cnx.org/content/m44390/latest/?collection=col11448/latest
OpenStax CNX
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SentencesMobile

The following tables show the resultant matrices populated with the atomic numbers.
The triplet quantum yields and lifetimes both decreased with increasing atomic number.
The number of protons in an atom is called its atomic number.
A left-hand subscript is sometimes used redundantly to indicate the atomic number.
Relativistic effects are important for the heavier elements with high atomic numbers.
Hydrogen ( H ) is the chemical element with atomic number 1.
Boron, with its atomic number of 5, is a very light element.
The heaviest element occurring in nature is uranium, with atomic number 92.
Elements having atomic numbers greater than that of uranium are called transuranic.
The first half of his thesis was his work with atomic numbers.
It's difficult to see atomic number in a sentence .
Atomic number is determined by the number of protons, and hence increases.
Lead ( Pb ) is atomic number 82, atomic weight 207.
Atoms on a periodic table are arranged in order of increasing atomic number.
The atomic number of an atom is usually about half its atomic mass.
Atomic Number : 106 Atomic Weight : [ 269 ] Melting Point :?
What you really mean is the atomic number of the atom.
QUESTION : What's the chemical element with the highest atomic number?
For now, they're known by their atomic numbers : 110, 111 and 112.
Atomic Number : 111 Atomic Weight : [ 281 ] Melting Point :?
As with other columns, reactivity decreases as the atomic number increases.