Bar Chart: How to adjust the font size for the bar labels as the chart size is manipulated

I have data that represents the binding energy of oxygen on different surfaces. Each bar is a different transition metal, and the length of the bar is the binding energy of oxygen. How do I make the font size of the labels larger while still keeping them centered on the bars?

The way I have it right now, the chart works when it is large enough. When it is too small, the font overlaps and does not look good?

newElementsSmall = {"Sc", "Ti", "V", "Cr", "Mn", "Fe", "Co", "Ni",
"Cu", "Zn", "Zr", "Nb", "Tc", "Ru", "Rh", "Pd", "Ag", "Hf", "Ta",
"Re", "Os", "Ir", "Pt", "Au"}

stackData = {-1.69071, -1.48652, -1.42055, -1.16451, -2.51796, \
-1.81939, -1.04659, -1.14478, -1.2814, -2.13397, -1.30394, -1.29924, \
-1.35072, -1.49208, -0.966458, -1.0429, -1.41273, -1.31235, -2.3501, \
-1.45391, -1.25234, -0.963033, -1.10553, -1.01026}

BarChart[ stackData, ChartLabels -> {Placed[newElementsSmall, Above]},
PlotLabel -> Style["6M1@32Ag", Bold, 50], ChartLegends -> {"eV"} ]


BarChart[stackData,