All the elements of a family in the periodic table have what feature in common? a) they all have similar chemical properties. b) they all have the same number of protons in the nucleus. c) they are all located in the same horizontal row or period. eliminate d) they all have the same number of electrons in the electron cloud.

The correct answer is A) They all have similar chemical properties.

Explanation:

In chemistry, the periodic table organizes visually the chemical elements. In this, elements are arranged according to different features. In the case of families of the elements, these refer to elements organized in the same column, for example, elements that are in column 18 form a family called noble gases.

These elements form a family because they have chemical properties; in the case of noble gases, this includes similar reactivity and physical features such as color and odor. Besides this, the elements of one family share a similar electron configuration but not the same number of electrons. This means, from the options given the one that identifies the elements that belong to a family is "They all have similar chemical properties".

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

4d^55s^1 ( third choice)