Mendeleev saw trends in the physical and chemical properties of elements when he organized them by .

atomic number

physical properties

atomic weight

density

atomic weight

Explanation:

Mendeleev realised that the physical and chemical properties of elements were related to their atomic weight

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8

explanation:

each principal energy level above the first contains one s orbital and three p orbitals. a set of three p orbitals, called the p sublevel, can hold a maximum of six electrons. therefore, the second level can contain a maximum of eight electrons - that is, two in the s orbital and 6 in the three p orbitals.

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