Images placed in the WYSIWYG editor should not be aligned using the alignment options in the toolbar or in the image properties window. To properly align an image, you should select the image, go to the style drop-down menu and select one of the following: image left (floats image left), image right (floats image right), image top and/or image center. This will apply the proper alignment styles to your image to ensure they look good on any device.
Please note that when applying the image left or image right class a "max-width" is also applied to your image. This allows the text around the image to flow properly as the layout adapts to various devices and sizes.