An element's atomic number is the number of protons in the nucleus of a single atom.The atomic number of an element or isotope can't be changed, so you can use it to figure out other characteristics, such as the amount of electrons and neutrons in an atom.
Step 1: There is a copy of the periodic table.
If you don't have one handy, we've got one here.The elements are ordered on a table according to their atomic numbers.Either memorize or find a copy of the periodic table.A periodic table is printed on the inside cover of most chemistry textbooks.
Step 2: You should find the element you're studying.
The full name of the elements and chemical symbol are included in most periodic tables.If you can't find it, look online for a chemical symbol followed by the element's name.
Step 3: The number is known as the atomic number.
The atomic number is usually found in the top left or top right corner of the element's box.This is always more than one number.Atomic mass is probably what you're looking at if the number includes a decimal point.
Step 4: It is confirmed based on nearby elements.
The table is arranged in chronological order.If your element's atomic number is "33", the left and right elements should be "32" and "34."You have definitely found the atomic number if this pattern holds true.There may be gaps after elements 56 and 88.The elements with atomic numbers are in two rows below the rest of the chart.They are separated to fit the periodic table in a more narrow shape.
Step 5: Understand the number.
A definition of an element's atomic number is the number of protons in one atom.This is how an element is defined.The total electric charge of the nucleus is determined by the number of protons and how many electrons the atom can support.Almost all of the element's physical and chemical properties are set by the atomic number.Every atom with eight protons is an oxygen atom.Two oxygen atoms might have different numbers of electrons, but they will always have eight protons.
Step 6: The atomic weight can be found.
The atomic weight is usually printed below the element name on the periodic table.The average mass of one atom is weighted to what you would find in nature.The number is in "atomic mass units".The term "relative atomic mass" is preferred by some scientists.
Step 7: To the mass number, round.
The mass number is the number of protons and neutrons in a single atom.This can be found by taking the atomic weight printed on the periodic table and rounding it to the nearest whole number.The electrons and protons are very close to 1 AMU.We're only interested in the whole numbers that tell us the number of protons and neutrons, not the precise measurement of the atomic weight.If you use the atomic weight, you will get an average for a typical sample.The average mass number of a bromine sample is 80, but a single atom almost always has a mass of 81.
Step 8: The number of electrons can be found.
The numbers of protons and electrons will be the same.If an atom loses electrons, it becomes an ion, which means that it is an electric charged atom.
Step 9: The number of neutrons is calculated.
You know the atomic number and mass number are related to the number of protons and neutrons.If you subtract the atomic number from the mass number, you can find the number of neutrons.The mass number of a single He atom is 4 and the atomic number is 2.It must have 4 and 2.A sample of silver has an average mass number of 108 and an atomic number 47.The average number of silver atoms in the sample is 48.
Step 10: Understand the radioactive elements.
A specific form of an element has a certain number of neutrons.Boron elements with a mass number of 10 are referred to in a chemistry problem.The values for "typical" boron should be used instead of this mass number.The atomic number stays the same.Every element has the same number of protons.