All plants need nitrogen to survive, but it is naturally available to them in only limited supplies. in 1909, engineers developed a process to make nitrogen available to plants by synthetically producing the chemical ammonia. once produced, ammonia could be used as a fertilizer for crops around the world to its nitrogen content. the process that the engineers developed is still used today. it makes use of the reaction between nitrogen gas and hydrogen gas at very high pressures. nitrogen gas is the most abundant gas in the atmosphere and is widely available. hydrogen gas needs to be made from the methane found in natural gas. natural gas is a fossil fuel that can be extracted from underground reserves. what natural resources are used to make ammonia fertilizers? 1)atmospheric nitrogen 2)ammonia 3)natural gas 4)hydrogen gas

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.

the awnser is group 12