Ammonia, nh3, has a higher melting point than pf3, despite the fact that melting point increases as you move down a group of elements in the periodic table. ammonia has a higher melting point because of the

Although, it is a fact that the melting point increases as you move down a group of elements in the periodic table, you cannot use this information for compounds since the type of bonds present in the compounds are another factor that would affect their properties. For this case, ammonia would have a higher melting point as compared to PF3 because of the presence of hydrogen bonding. PF3 only has dipole-dipole forces which is much weaker as compared to a hydrogen bond. Hydrogen bonding is a special type of dipole forces which is a result of the electronegativity of a hydrogen atom and a very electronegative atom.

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer