The Modern Periodic Table has 18 vertical columns known as ‘groups’ and ________ horizontal rows known as ‘periods’.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 7.
The Modern Periodic Table has 18 vertical columns known as ‘groups’ and 7 horizontal rows known as ‘periods’. Groups represent elements with similar chemical properties due to having the same number of valence electrons, while periods indicate the number of electron shells an element has. This arrangement helps in understanding the periodic trends in properties like atomic size, electronegativity, and reactivity.