Use the drop-down menus to complete each sentence. elements in the same have the same number of valence electrons. elements in the same have the same number of electron shells. metallic elements become reactive as you move left to right in a period. metallic elements become reactive as you move top to bottom in a gr

1) elements in the same group have the same number of valence electrons.

for example halogens have 7 valence electrons.

group 17 (halogens) elements are: fluorine (f), chlorine (cl), bromine (br) and iodine (i). they are very reactive and easily form many compounds.

2) elements in the same period have the same number of electron shells.

for example all elements in period 2 have two electron shells.

3) metallic elements become less reactive as you move left to right in a period.

for example, magnesium (right) is less reactive than sodium (left).

4) metallic elements become more reactive as you move top to bottom in a group.

for example, potassium (down in group 1) is more reactive than sodium (up in group 1).

the answer is 303.15 or 303

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.