Which statement best describes the reaction pathway graph for an exothermic reaction but not an endothermic reaction?
It has a hill in the middle that is the highest point.
It has a valley in the middle that is its lowest point.
The reactants are higher in energy than the products.
The products are higher in energy than the reactants.

Explanation:

Any chemical reaction can be classified into either exothermic or endothermic.

Let us understand the term:

1. exothermic: Heat released to the environment is called exothermic

2. endothermic: Heat absorbed from the environment is called endothermic

According to the pathway diagram, we can say that "reactants are higher in energy than the products". Here in the given diagram, only less energy is required thus resulting in energy being released which is considered as exothermic.

Thus we can conclude that "the reactants are higher in energy than the products".

The reactants are higher in energy than products

Explanation:

exothermic reactions release energy meaning that the reactants need to have a higher energy than the products

- both b and d.

-since b and d are the closest coastlines then that makes it the most affected.

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assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.