elements placed...?

Question

elements placed in horizontal rows on the Periodic Table are called:
A) periods
B) families
C) isotopes
D) metalloids

Answer 1

A)periods

There are 7 periods in the modern long form of periodic table.

Answer 2

Groups and periods
A period is a horizontal row in the periodic table of the elements.
Although groups are the most common way of classifying elements, there are some regions of the periodic table where the horizontal trends and similarities in properties are more significant than vertical group trends. This can be true in the d-block (or "transition metals"), and especially for the f-block, where the lanthanides and actinides form two substantial horizontal series of elements.

A group, also known as a family, is a vertical column in the periodic table of the elements.
Groups are considered the most important method of classifying the elements. In some groups, the elements have very similar properties and exhibit a clear trend in properties down the group — these groups tend to be given trivial (non-scientific) names, e.g. the alkali metals, alkaline earth metals, halogens and noble gases. Some other groups in the periodic table display fewer similarities and/or vertical trends (for example Groups 14 and 15), and these have no trivial names and are referred to simply by their group numbers. Modern quantum mechanical theories of atomic structure explain group trends by proposing that elements within the same group have the same electron configurations in their valence shell, which is the most important factor in accounting for their similar properties.

Answer 3

periods

Answer 4

families