5 Simple Ways To Identify An Element On The Periodic Table

Atomic number is abbreviated “Z”. If your homework says an element has Z=13, you can look for atomic number 13 on the periodic table and identify it as aluminum (Al). An atom can gain or lose neutrons and still be the same element. For instance, 1122Na{\displaystyle _{11}^{22}Na} is a sodium atom with 11 protons and 22 neutrons. If it gains a neutron, it is still sodium and becomes 1123Na{\displaystyle _{11}^{23}Na} (with 23 neutrons). But if you add a proton, it transforms from sodium to magnesium, 12Mg{\displaystyle _{12}Mg}.

For example, if you are asked which element has 8 electrons, look for the element with atomic number 8: oxygen. For a more advanced example, the configuration 1s22s22p2{\displaystyle 1s^{2}2s^{2}2p^{2}} has 2{\displaystyle ^{2}} electrons in the 1s shell, 2{\displaystyle ^{2}} in the 2s shell, and 2{\displaystyle ^{2}} in the 2p shell, for a total of 2+2+2=6. This is carbon, with atomic number 6. Note that this only holds true when the atoms are in electrically neutral states, not ionized. But unless specified otherwise, this is the state we talk about when we discuss element characteristics. [3] X Research source

The first row (hydrogen and helium) fills up the 1s orbital from left to right. Think of these, plus all elements in the first two columns, as the “s-block”. Each row of the “s-block” fills up one s orbital. The right-hand side of the table is the “p-block”, starting with boron through neon. Each row of the “p-block” fills up one p orbital (starting with 2p). The transition metals in the center form the “d-block”. Each row fills up one d orbital, starting with scandium through zinc filling 3d. The lanthanides and actinides at the bottom of the table fill the 4f and 5f orbitals. (Some elements here break the pattern, so double-check these. [5] X Research source ) For example, look at [Kr]5s24d105p2{\displaystyle [Kr]5s^{2}4d^{10}5p^{2}} and focus on the last orbital: 5p2{\displaystyle 5p^{2}}. Go to the “p-block” on the right, and count rows down from 2p (boron) until you reach 5p (indium). Since this element has two electrons in 5p, count two elements into this row of the p-block to get the answer: tin.

For example, a lithium spectrum has a very bright, thick green line, and several other fainter ones in different colors. If your spectrum has all those same lines on it, the light came from the element lithium. [7] X Research source (Some types of spectra will show dark gaps instead of bright lines, but you can compare these the same way. ) Want to know why this works? Electrons only absorb and emit light at very specific wavelengths (meaning specific colors). Different elements have different arrangements of electrons, which leads to different colors of bands. [8] X Research source A more advanced spectroscope shows a detailed graph instead of a few lines. You can match the x-axis value at each peak to a table of known values to identify molecules. As you learn about different types of molecules, you’ll learn to focus on just a few useful spots on the graph to save time. [9] X Research source

Let’s say the tallest bar is at m/z 18, with short bars at 1, 16, and 17. Only two of these match the atomic mass of an element: hydrogen (atomic mass 1) and oxygen (atomic mass 16). Adding these atoms together gives you the compounds HO (mass 1 + 16 = 17) and H2O (mass 1 + 1 + 16 = 18). This sample was water![11] X Research source Technically, a mass spectrometer ionizes the sample and sorts by the ratio of mass to charge (or m/z). But most ions will have a charge of 1, and so you can ignore the division problem and just look at mass. The smallest bars often represent small amounts of more charged particles that you can ignore for identification purposes. [12] X Research source