What does the atomic number of an element mean?

Answer 1

The number of protons or electrons an atom has.

The periodic table is organised by the atomic number. If you look at it, you will see it begin at hydrogen with #1#, then #2#, helium, #3#, lithium, #4#, beryllium, and so on. The atomic number is what number atom it is.

In a scientific sense, the atomic number is the number of protons you find in the nucleus of the atom, or the number of electrons floating around the outside. Protons and electrons come in the same number in atoms. (Ions are where the electron number differs from protons.)

For example, in lithium, the atomic number is #3#, which means it has #3# protons in the nucleus and #3# electrons around the outside. In ionic lithium, it loses an electron and ends up with only #2# electrons, though the number of protons remains the same at #3#.

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Answer 2

Xavier Avery

An element's atomic number, which establishes both the element's identity and its place in the periodic table, is the number of protons contained in the nucleus of an atom of that element.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.