What are the first 20 items

A common chemical problem is to name or even memorize the first 20 elements and their symbols. The elements are arranged in the periodic table according to increasing atomic number. This is also the number of protons in each atom.

These are the first 20 items, listed in order:

  1. H - hydrogen
  2. He - helium
  3. Li - lithium
  4. Be - beryllium
  5. B - boron
  6. C - carbon
  7. N - nitrogen
  8. O - oxygen
  9. F - fluorine
  10. Ne - neon
  11. Na - sodium
  12. Mg - magnesium
  13. Al - aluminum
  14. Si - silicon
  15. P - phosphorus
  16. S - sulfur
  17. Cl - chlorine
  18. Ar - argon
  19. K - potassium
  20. Ca - calcium

Element symbols and numbers

The number of the element is its atomic number, that is, the number of protons in each atom of this element. The element symbol is a one- or two-letter abbreviation of the element name. Sometimes it refers to an ancient name. (For example, K is for potassium.)

The element name can tell you something about its properties.

  • Items with names starting with - gene are non-metals that are gases in pure form at room temperature.
  • Elements whose names start with - ine ends belong to a group of elements known as halogens. Halogens are extremely reactive and easily form compounds.
  • Element names starting with - on are noble gases that are inert or non-reactive gases at room temperature.
  • Most element names end with - ium . These elements are metals that are usually hard, shiny, and conductive.

What one Not of an element's name or symbol tell how many neutrons or electrons an atom has. To know the number of neutrons, you need to know the isotope of the element. This is indicated by numbers (superscript, subscript, or after the symbol) to indicate the total number of protons and neutrons.

For example, carbon-14 has 14 protons and neutrons. Knowing that all carbon atoms have 6 protons, the number of neutrons is 14 - 6 = 8. Ions are atoms with different numbers of protons and electrons. Ions are indicated by a superscript after the element symbol, which indicates whether the charge on the atom is positive (more protons) or negative (more electrons), and the amount of charge. For example, approx 2+ the symbol for a calcium ion with a positive 2-charge. Since the atomic number of calcium is 20 and the charge is positive, it means that the ion has 20 - 2 or 18 electrons.

Chemical elements

To be an element, a substance must have at least protons, as these particles define the nature of the element. Elements are made up of atoms that contain a nucleus of protons and neutrons surrounded by a cloud or shell of electrons. Elements are considered to be the basic building blocks of matter because they are the simplest form of matter that cannot be divided by chemical means.

Learn more

Knowing the first 20 elements can help you become familiar with the elements and the periodic table. Next, check out the full list of items and learn how to memorize the first 20 items. Once you are comfortable with the elements, test yourself by taking the 20 elements icon quiz.