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What are the periodic trends for atomic number and atomic mass?

Answer 1

The atomic number increases across a period and down the group or family. The atomic mass generally increases with atomic number with a few exceptions.

The atomic mass is the sum of the protons and neutrons; as the atomic number increases, the atomic mass increases as well. Occasionally, there is not a corresponding increase in the number of neutrons. The atomic number is the number of protons in an atom, and it is the basis for the periodic table. Therefore, the atomic number increases with each element.

For instance, atomic number 18 in argon has a mass of 40 due to its 22 neutrons, whereas number 19 in potassium has a mass of 39 due to its mere 20 neutrons.

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Answer 2

Wyatt Atkins

Atomic number increases across a period and down a group. Atomic mass generally increases across a period and down a group, but there are exceptions due to isotopic abundances.

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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.