About the Atom Calculator
The atom calculator is a tool for calculating the atomic number and the mass number based on the number of atom components - protons, neutrons, and electrons (or vice versa). In addition, you can define the charge of ions with known numbers of protons and electrons.
What is an Atom?
An atom is the smallest constituent unit of matter that retains the properties of an element. A typical atom consists of a nucleus and electron cloud. Atom components are positively-charged protons and electrically neutral neutrons in the nucleus with negatively-charged electrons orbiting this nucleus. Protons and neutrons are called nucleons.
Atoms are electrically neutral because they possess an equal number of electrons and protons. However, when an atom has an unequal number of protons and electrons, it has an electrical charge and creates ions.
- If an ion has more protons than electrons, it is positively charged and is called a cation.
- Conversely, if an ion has more electrons than protons, it is negatively charged and is called an anion.
Atomic Number and Mass Number
An atom is uniquely identified with the atomic number Z. The atomic number is the number of protons present in the nucleus. In the case of uncharged atoms, the atomic number is equal to the number of electrons.
In contrast, in ions, the number of electrons is the difference between the atomic number and the charge of ions. In cations, there are fewer electrons than protons, while in anions, there are more electrons than protons.
The number of neutrons in a given element can vary. The variants of the same chemical element with a different number of neutrons are called isotopes. Protons and neutrons determine the mass of an atom. Mass number symbol A is the sum of the number of protons and neutrons.
Calculation Formulas
If you know the atomic number (Z), atomic mass (A), and charge (z), you can calculate the numbers of protons (p), neutrons (n), and electrons (e):
p = Z
n = A - Z
e = Z - z
On the other hand, if you know the number of protons (p), neutrons (n), and electrons (e), you can calculate the atomic number (Z), atomic mass (A), and charge (z):
Z = p
A = p + n
z = p - e
Example Calculations
Example 1: Sodium Atom
Given: Sodium (Na), Charge = 0
Atomic number (Z) = 11, Mass number (A) = 23
Calculate particles:
p = 11 (protons)
n = 23 - 11 = 12 (neutrons)
e = 11 - 0 = 11 (electrons)
Example 2: Sulfide Anion
Given: p = 16, n = 16, e = 18
Calculate properties:
Z = 16 (atomic number - Sulfur)
A = 16 + 16 = 32 (mass number)
z = 16 - 18 = -2 (charge)
Common Questions (FAQs)
What are atoms made of?
Atoms are made of three kinds of particles: neutrons, protons, and electrons. Protons and neutrons form the nucleus of the atom, and electrons circulate around the nucleus. Electrons are negatively charged, and protons are positively charged. Normally, an atom is electrically neutral because the number of protons and electrons are equal.
Which elementary particle gives an atom its identity?
The number of protons gives an atom its identity. Protons are positively charged particles that are found in the nucleus of an atom. No two elements have the same number of protons. An atom with 1 proton is a hydrogen atom; an atom with 11 protons is a sodium atom, and so on.
What is the mass number of an atom of helium that contains 2 neutrons?
The mass number is 4. The number of neutrons is 2, and the helium atom always has 2 protons (check the atomic number 2 of helium). Thus, the mass number is the sum of protons and neutrons in the nucleus: 2 + 2 = 4.