Final answer:
The atomic number increases from left to right within a period and from top to bottom within a group. Number of energy levels increases from top to bottom within a group, but remains constant across a period. These trends reflect the arrangement of elements in the periodic table with respect to atomic numbers and energy levels.
Step-by-step explanation:
The question pertains to periodic trends of elements in the periodic table, specifically in relation to atomic numbers and energy levels within periods and groups. Here's how each statement reflects changes:
a. Atomic number increases from left to right within the same period.
b. Number of energy levels increases from top to bottom within the same column as additional shells are added.
c. Atomic number increases from top to bottom within the same column, with each subsequent element having a higher atomic number.
d. Number of energy levels stays the same from left to right within the same period since all elements in a period have electrons in the same highest principal energy level.
The periodic table is a tool that organizes elements according to increasing atomic numbers, and elements with similar properties are grouped together in columns, known as groups. When you move from left to right across a period, the atomic number of the elements increases. In contrast, moving down a group increases the number of energy levels because additional shells are present. Moreover, across a period, the atomic radii decrease due to an increase in nuclear charge, which attracts the electrons closer.