How many groups are in the modern periodic table? A:12

B:18

C:22

D:24

B: 18

Explanation:

A group is a vertical column of the periodic table based on the organization of the outer shell electrons.  There are a total of 18 groups. From left to right in the periodic table, there are two groups (1 and 2) of elements in the hydrogen block, ten groups (3 through 12) in the transition block, and six groups (13 through 18) in the main block. The elements in the inner-transition block (lanthanoids and actinoids) are not given group numbers.

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what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.