Question

Which of the following always decreases down a group a 2nd period, 8th group b 3rd period, 8th group c 2nd period, 18th group d 3rd period, 18th group​

Answer 1

Explanation:

period in the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law. For example, the halogens lie in the second-last column (group 17) and share similar properties, such as high reactivity and the tendency to gain one electron to arrive at a noble-gas electronic configuration. As of 2021, a total of 118 elements have been discovered and confirmed.