Consider the group 1a elements sodium (period 3), potassium (period 4), and rubidium (period 5). what would you predict about the ionization energies of these elements? na < k < rb na > k > rb c. rb < na < k d. na = k = rb

The correct answer is Na > K > Rb.  

The order predicted would be ionization energy of sodium is greater than the ionization energy of potassium, which is greater than the ionization energy of rubidium.  

The ionization energy refers to energy, which has to be supplemented to a gaseous atom in order to withdraw an electron and produce a positive ion. The ionization energy decreases in going down a group. The cause of the decline of the ionization energy down a group is that as one moves down a group, the size of the atom increases that signifies that the valence electrons get further away from the nucleus, and thus, less energy is required to withdraw the electrons.  

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

plants need sunlight, water, and carbon dioxide to make food. plants use the raw materials of water, nutrients they absorb from soil, and carbon dioxide to make sugars the plant can use. energy from the sun and chlorophyll are also needed.