1.What is the total energy change for the following reaction: H2 + I2 -> 2HI?

Given:
H-H bond: 436 kJ/mol
I-I bond: 151 kJ/mol
H-I bond: 297 kJ/mol
A. +297 kJ/mol
B. +7 kJ/mol
C. -7 kJ/mol
D. -290 kJ/mol
2.While camping you light a small campfire, initiating the combustion of wood to produce heat and light. What can you determine about this reaction?
A. It is endothermic.
B. The bond breaking energy is more than 600 kJ.
C. It is exothermic.
D. The bond making energy is more than 600 kJ.
3.Activation energy is:
A. None of these.
B. The maximum amount of energy reactants can hold.
C. The energy needed to begin breaking the bonds of products.
D. The energy needed to begin breaking the bonds of reactants.
4.Sodium hydroxide and water will react at room temperature. What does this indicate about its activation energy?
A. The reaction cannot reach activation energy.
B. The activation energy is very high.
C. The activation energy is at exactly 600 kJ.
D. The activation energy is very low.

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.