1. what trends do you see when considering total electrons, valence electrons (highest occupied energy level/outermost level electrons), periods, sublevels, blocks, and groups/ families?

Explanation:

Elements in the same group have the same number of valence electrons. Across a period left to right number of valence shell electrons increases but in the group this trend remains same means number of valence shell electrons are constant.

The atomic radius is increases from top to bottom in the group and decreases from left to right across a period.

Ionization enthalpy or energy increases across a period and decreases down the group. Ionization energy is the energy that requires to remove the outermost electron from the subshell.

Electronegativity decreases down the group because atomic number increases down the group and increases across a period.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

the answer is d. 74.02