Try skipinitialspace:
In [26]: pd.read_table('test.txt', sep=' ', skipinitialspace=True)
Out[26]:
<class 'pandas.core.frame.DataFrame'>
Int64Index: 386 entries, 0 to 385
Data columns (total 7 columns):
Mon 386 non-null values
id 386 non-null values
NA 386 non-null values
alpha_K24 386 non-null values
class 386 non-null values
alpha_K8 386 non-null values
class.1 0 non-null values
dtypes: float64(3), object(4)
EDIT
Sorry for misunderstanding your problem. I think you can read the table as @DSM mentioned and also set the column names
In [55]: pd.read_table('test.txt', sep=r"\s\s+", header=None, skiprows=[0], names=['Mon id', 'Na', 'alpha_K24', 'class', 'alpha_8', 'class'])
Out[55]:
<class 'pandas.core.frame.DataFrame'>
Int64Index: 386 entries, 0 to 385
Data columns (total 6 columns):
Mon id 386 non-null values
Na 386 non-null values
alpha_K24 386 non-null values
class 386 non-null values
alpha_8 386 non-null values
class 386 non-null values
dtypes: float64(2), object(4)
Note that you might set your second class as another name. Or you'll get two columns by df['class']